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.

rust/collector/src/web/cache.rs

@@ -1,4 +1,5 @@
-//! Stale-while-revalidate response cache, as `_cached_swr` in src/web_api.py:
+//! Stale-while-revalidate response cache, as the retired FastAPI app's
+//! `_cached_swr`:
 //!
 //! - fresh entry: served;
 //! - expired entry (no older than `max_stale`): served at once, marked stale,

rust/collector/src/web/mod.rs

@@ -1,8 +1,9 @@
-//! The website and read API: the port of the FastAPI app (src/web_api.py).
+//! The website and read API: the port of the retired FastAPI app.
 //!
 //! Same routes, parameters, JSON fields, status codes, cache headers and
-//! response caches as the Python app, checked route by route against it by
-//! scripts/api_parity.py. It runs inside `ping-collector run` (WEB_LISTEN)
+//! response caches as the Python app had; before the cutover (2026-10-18) a
+//! route-by-route comparison of the two on production data found no
+//! difference. It runs inside `ping-collector run` (WEB_LISTEN)
 //! or alone (`ping-collector serve`). /docs is the same Swagger UI, fed by an
 //! OpenAPI document built from the route table that also validates the
 //! parameters (openapi.rs, params.rs).

rust/collector/src/web/tests.rs

@@ -1,7 +1,7 @@
 //! Route tests: the router as the server runs it, against a throwaway
 //! schema (TEST_DATABASE_URL; see db_tests.rs) or, for the routes that do
 //! not touch the database, a pool that never connects. Output formats are
-//! the FastAPI app's (scripts/api_parity.py compares the two live).
+//! the retired FastAPI app's (field order, isoformat, errors).
 
 use super::{AppState, router};
 use crate::config::Config;