chore: remove the Python service; Python is the training stack only

Phase 4 of docs/RUST_REWRITE.md. Since 2026-10-18 ping-collector (rust/)
collects, forecasts, notifies (ntfy + Matrix) and serves the website/API;
nothing in production ran the Python service code any more.

Removed (~17k lines): the FastAPI app (web_api, schemas, health_check,
metrics, postgres_history, forecast_history, thaiwater), the Python RID
collector and CLI (water_scraper_v3, main, run.py), the notifier and Matrix
alerting (notify, alerting), the multi-backend adapters (SQLite, MySQL,
InfluxDB, VictoriaMetrics) with demo databases, models/validators/exceptions/
logging/rate limiter, ml/skill.py (served by Rust now), the migration tooling
(api_parity, collector_parity, e2e_notify, install_collector.sh,
gen_notify_cases.py, spikes/rust-forecast), Docker/compose/Grafana files,
sql/, the release workflow and the docs for all of that. Their tests went
with them.

Kept in Python: src/ml (training, evaluation harness, export; predict.py as
the reference the Rust forecaster is tested against), the HII and RID-dam
clients/stores for the archive backfills (their live collectors removed),
the backfill scripts, retrain.sh + timer, forecast_parity.py.

- PostgreSQL only: src/config.py is database_url() from POSTGRES_* / .env;
  the stores lost their sqlite/mysql branches (and the 2026-08 column
  migration). The database tests run against a throwaway schema from
  TEST_DATABASE_URL (tests/conftest.py pg_url, skipped without it), as the
  Rust tests do; CI gets a PostgreSQL service. 100 tests (66 without a DB).
- The notifier settings moved from src/notify.py into src/ml/export.py;
  flood_config.json regenerates byte-identical.
- tests/test_dashboard.py checks every path the dashboard fetches against
  ping-collector's router.
- Dependencies: fastapi, uvicorn, pydantic, influxdb, pymysql, psutil,
  schedule, sphinx, pyinstaller, mypy, pytest-asyncio dropped; python-dotenv
  1.1.1 explicit (it came in through uvicorn[standard]).
- Formatting contract extended to scripts/ and tests/ (reformatted once).
- scripts/install.sh is the one installer (fresh host or update, in place in
  a checkout without touching its ownership): binary, units, uv sync, .env
  defaults, removes the retired water-monitor.service and any old
  --alert-check cron job, dry run + forecast check, restart, readiness wait.
- Docs, CLAUDE.md, CONTRIBUTING.md, .env.example, Makefile, unit comments
  and Rust doc comments updated to the Rust service.

CLAUDE.md

@@ -5,16 +5,20 @@ Guidance for AI coding agents working in this repository.
 ## What this is
 
 Flood monitoring and forecasting for the Ping River, Chiang Mai. Public dashboard and
-API at https://water.buildfor.life/ (never publish the server's private/Tailscale IP).
-Production: one systemd unit on a small VPS, `/opt/thailand-water-monitor`, user
-`water-monitor`, interpreter `.venv/bin/python` (uv-managed), updated by `git pull`.
+API at https://water.buildfor.life/ (never publish the server's private/mesh IP).
+Production: one systemd unit, `ping-collector.service` (the Rust binary in `rust/`),
+on a small VPS in `/opt/thailand-water-monitor` (a git checkout), user `water-monitor`;
+plus the monthly `water-monitor-retrain.timer` (Python, `.venv`, uv-managed). Updated by
+`git pull`, `cargo build --release`, `sudo bash scripts/install.sh`.
 
 ## Rules
 
 - Python 3.11 only. `uv sync --python 3.11`; run everything as `uv run ...`.
-- `make format` (black 88 / isort black profile, config in pyproject.toml) before
-  committing; CI fails on formatting. `make test` must stay green — tests are
-  synthetic-data only, never add one that needs the DB or network.
+- `make format` (black 88 / isort black profile, config in pyproject.toml; cargo fmt)
+  before committing; CI fails on formatting. `make test` must stay green. Tests use
+  synthetic data, never the network; database tests (both languages) run against a
+  throwaway PostgreSQL schema from `TEST_DATABASE_URL` and skip without it.
+- PostgreSQL only. No other database backends.
 - Timestamps everywhere are Asia/Bangkok wall-clock with no offset. The dashboard
   parses them with `parseTs()` and renders with `timeZone: TZ`; keep it that way.
 - Model changes go through the rolling-origin harness (`scripts/evaluate_variants.py`)
@@ -27,37 +31,41 @@ Production: one systemd unit on a small VPS, `/opt/thailand-water-monitor`, user
   before. Stage files by name.
 - Do not add Co-Authored-By trailers.
 - The dashboard is a single file, `src/static/dashboard.html`, EN + TH via the `t()`
-  table: every user-visible string needs both languages.
+  table: every user-visible string needs both languages. Every path it fetches must be
+  a route in `rust/collector/src/web/mod.rs` (tests/test_dashboard.py checks).
 - Rust (`rust/`, see rust/README.md): `cargo fmt --all`, `cargo clippy --all-targets
-  -- -D warnings`, `cargo test` (database tests need `TEST_DATABASE_URL`). The Rust
-  collector writes the same tables as the Python collectors: a change to a table,
-  upsert or parser on one side must be made on the other until the Python side is
-  retired (check with a live run of both into two databases).
-- The forecast is served by Rust (`rust/forecast`) from models trained in Python.
-  A change to `src/ml/features.py`, `predict.py`, the HII fill or the dam frame
-  must be ported in the same change: regenerate
-  `rust/forecast/testdata/gen_forecast_fixtures.py` and keep
-  `cargo test -p ping-forecast` green. Changing thresholds, stages, leads or
-  notify constants: `uv run python -m src.ml.export --config` (a test fails
-  otherwise) and rebuild the collector. Notify texts:
-  `rust/collector/testdata/gen_notify_cases.py`.
-- API routes live in `rust/collector/src/web` (phase 3). Until the FastAPI app is
-  removed, a route change goes into both, and `scripts/api_parity.py` (both
-  servers on one database) must report no differences. A route's parameters are
-  declared once (`web/params.rs`); that list validates and documents (/docs).
+  -- -D warnings`, `cargo test`; minimum version 1.88
+  (`CARGO_TARGET_DIR=target/msrv cargo +1.88 check --all-targets --locked`). Read
+  `.env` only through `rust/collector/src/envfile.rs` (python-dotenv semantics, never
+  dotenvy: the Python tools read the same file).
+- The forecast is served by Rust (`rust/forecast`) from models trained in Python;
+  `src/ml/predict.py` is the reference it is tested against. A change to
+  `src/ml/features.py`, `predict.py`, the HII fill or the dam frame must be ported in
+  the same change: regenerate `rust/forecast/testdata/gen_forecast_fixtures.py` and keep
+  `cargo test -p ping-forecast` green. Changing thresholds, stages, leads or the
+  notifier settings (`src/ml/export.py`): `uv run python -m src.ml.export --config`
+  (a test fails otherwise) and rebuild the collector.
+- Notifier texts are pinned by `rust/collector/testdata/notify_python_cases.json.gz`;
+  a deliberate wording change updates that fixture in the same commit.
+- API routes live in `rust/collector/src/web`. A route's parameters are declared once
+  (`web/params.rs`); that list validates and documents (/docs). Keep response formats
+  stable: external clients use them.
+- The Python backfill stores (`src/hii_collector.py`, `src/rid_reservoir.py`,
+  `src/ml/rain.py`) write the same tables as `rust/collector/src/db.rs`: a table or
+  upsert change goes into both.
 
 ## Where things are
 
-- `src/web_api.py` FastAPI app; `src/water_scraper_v3.py` RID collector;
-  `src/hii_collector.py` ThaiWater/HII; `src/ml/` features/train/evaluate/predict,
-  `rain.py` (Open-Meteo), `dam.py`, `hii_rain.py`.
-- `scripts/retrain.sh` + `water-monitor-retrain.timer`: monthly retrain with staged
-  promote. `scripts/dev_proxy.py`: serve the working-copy dashboard against the live API.
-- `rust/collector` (`ping-collector`): Rust data collector; with it deployed the
-  Python app runs `COLLECTION_ENABLED=false`. With `FORECAST_IN_COLLECTOR=true` it
-  also forecasts (`rust/forecast`) and sends ntfy + Matrix; with `WEB_LISTEN` it
-  serves the website and API (`rust/collector/src/web`, the port of
-  `src/web_api.py`; the dashboard stays `src/static/dashboard.html`). Rewrite
-  plan: `docs/RUST_REWRITE.md`.
+- `rust/collector` (`ping-collector`): collection (`rid.rs`, `hii.rs`, `dams.rs`,
+  `rain.rs`), forecast run (`forecasting.rs`), ntfy/Matrix (`notify.rs`), website/API
+  (`web/`), tables (`db.rs`). `rust/forecast`: inference.
+- `src/ml/`: features/train/evaluate/predict/export, `rain.py` (Open-Meteo), `dam.py`,
+  `hii_rain.py`. `src/hii_backfill.py`, `src/hii_collector.py`, `src/rid_reservoir.py`:
+  archive backfills (`scripts/backfill_*.py`).
+- `scripts/install.sh`: install/update on the server. `scripts/retrain.sh` +
+  `water-monitor-retrain.timer`: monthly retrain with staged promote.
+  `scripts/forecast_parity.py`: Rust vs Python forecast on a live database.
+  `scripts/dev_proxy.py`: serve the working-copy dashboard against the live API.
 - `docs/FLOOD_FORECASTING.md` is the authoritative model write-up; `docs/DATA_SOURCES.md`
-  the source catalog.
+  the source catalog; `docs/NOTIFICATIONS.md` the alerts; `docs/RUST_REWRITE.md` the
+  history of the Python-to-Rust move.