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.

scripts/dev_proxy.py

@@ -25,18 +25,29 @@ class Handler(http.server.BaseHTTPRequestHandler):
                 self._send(200, "application/json", Path(file).read_bytes())
                 return
         if self.path.startswith("/static/"):
-            f = STATIC / self.path[len("/static/"):].split("?")[0]
+            f = STATIC / self.path[len("/static/") :].split("?")[0]
             if f.is_file():
-                ctype = "application/json" if f.suffix in (".json", ".geojson") else "application/octet-stream"
+                ctype = (
+                    "application/json"
+                    if f.suffix in (".json", ".geojson")
+                    else "application/octet-stream"
+                )
                 self._send(200, ctype, f.read_bytes())
                 return
         try:
             req = urllib.request.Request(
                 UPSTREAM + self.path,
-                headers={"User-Agent": "Mozilla/5.0 (dev_proxy; +https://buildfor.life)", "Accept": "application/json"},
+                headers={
+                    "User-Agent": "Mozilla/5.0 (dev_proxy; +https://buildfor.life)",
+                    "Accept": "application/json",
+                },
             )
             with urllib.request.urlopen(req, timeout=60) as r:
-                self._send(r.status, r.headers.get("Content-Type", "application/json"), r.read())
+                self._send(
+                    r.status,
+                    r.headers.get("Content-Type", "application/json"),
+                    r.read(),
+                )
         except urllib.error.HTTPError as e:
             self._send(e.code, "application/json", e.read())