feat(strava): add per-user BYO-OAuth workout source + Garmin indirect-path docs

Add Strava as a per-user BYO-OAuth workout source, mirroring the shipped
WHOOP/Oura/Polar pattern. Strava caps every new app at single-player mode, so
each self-hoster registers their own app and pastes the client id/secret into
Settings (falling back to a shared env app). Strava is a workout source only —
it exposes no daily metrics and no training-depth analytics are derived.

- Schema (migration 0233): per-user encrypted client id/secret + access/refresh
  tokens, plaintext athlete id, incremental cursor, and backfill marker on
  `User`; `STRAVA` added to `MeasurementSource`.
- Token model follows Oura's reactive-refresh-on-401 with a compare-and-set on
  the stored refresh ciphertext, because Strava rotates its refresh token on
  every refresh.
- Client over safeFetch: authorization-code + refresh, activity list + budget-
  aware per-activity detail (for calories/HR), honouring the 200/15min cap; each
  activity maps to one `Workout` row. Activity name/description stay in metadata
  as data, never surfaced or interpolated.
- Dedup reuses the existing source-agnostic two-layer picker: `STRAVA` slots
  into the workout ladder below the device-native wearables and above
  MANUAL/IMPORT, so an Apple-Watch + Strava twin collapses to one canonical row.
- Poll-cohort hourly sync (:17) + self-converging boot backfill, wired into the
  integration-sync registrar. Webhook deferred.
- OAuth routes (connect/callback/credentials/disconnect/status/test) with signed
  state, cross-account re-auth rejection, and a surgical `www.strava.com`
  connect-src gated to the Strava surfaces.
- Settings card + consolidated status envelope entry; env + compose whitelist;
  i18n across all six locales.
- Garmin: no direct connector is possible (business-partner-only). Add
  docs/integrations/garmin.md documenting the Apple Health / Google Health
  Connect path and Garmin's withheld proprietary scores, cross-linked from both
  platform docs, plus a non-connector info note in the Connections panel.

Regenerate docs/api/openapi.yaml for the new `STRAVA` MeasurementSource value.

src/proxy.ts

@@ -410,6 +410,15 @@ export function proxy(request: NextRequest) {
     pathname.startsWith("/settings/integrations/whoop") ||
     pathname.startsWith("/api/whoop/");
   const whoopConnectSrc = isWhoopRoute ? " https://api.prod.whoop.com" : "";
+  // v1.28.x — `www.strava.com` gated to the Strava settings surface +
+  // `/api/strava/*`, mirroring the WHOOP gating shape. The Strava data client
+  // lives server-side and the OAuth handshake is a browser redirect (not a
+  // fetch), so this is belt-and-suspenders parity — no other surface ever needs
+  // to reach the Strava host from the browser.
+  const isStravaRoute =
+    pathname.startsWith("/settings/integrations/strava") ||
+    pathname.startsWith("/api/strava/");
+  const stravaConnectSrc = isStravaRoute ? " https://www.strava.com" : "";
   // v1.5.5 — Gravatar host removed from `img-src`. The /me payload
   // used to return `gravatarUrl: https://www.gravatar.com/avatar/<sha256(email)>`,
   // which leaked the email digest to Automattic on every authenticated
@@ -433,7 +442,7 @@ export function proxy(request: NextRequest) {
       `default-src 'none'; frame-ancestors 'self';`
     : isDev
       ? `default-src 'self'; script-src 'self' 'unsafe-eval' 'unsafe-inline'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; connect-src 'self'; font-src 'self';`
-      : `default-src 'self'; script-src 'self' 'nonce-${nonce}'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; connect-src 'self'${aiConnectSrc}${withingsConnectSrc}${whoopConnectSrc}; font-src 'self'; object-src 'none'; base-uri 'self'; form-action 'self'; frame-ancestors 'none'; worker-src 'self'; report-uri ${cspReportEndpoint}; report-to csp-endpoint;`;
+      : `default-src 'self'; script-src 'self' 'nonce-${nonce}'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; connect-src 'self'${aiConnectSrc}${withingsConnectSrc}${whoopConnectSrc}${stravaConnectSrc}; font-src 'self'; object-src 'none'; base-uri 'self'; form-action 'self'; frame-ancestors 'none'; worker-src 'self'; report-uri ${cspReportEndpoint}; report-to csp-endpoint;`;
   response.headers.set("Content-Security-Policy", csp);
 
   // Production-only headers. HSTS carries `preload` so the domain stays