feat(journal): Garmin activity import — provider, webhook pipeline, backfill (§1–5)

Garmin Connect as the third connected-services provider (spec:
garmin-import). The interesting parts:

- Push-first ingestion: Garmin has no list endpoint. The webhook
  normalizes ping (callbackURL) and push (inline) notification batches
  into events; the slow work (authorized FIT download, FIT→GPX via the
  shared converter, activity creation) runs in a garmin-import-activity
  pg-boss job so the webhook answers fast. Callback URLs are validated
  against Garmin's API host before any fetch (SSRF guard).
- History via backfill requests: /sync/import/garmin is a date-range
  requester with honest async progress (no pick list — the concept
  doesn't exist in a push model). Ranges chunk to Garmin's 90-day cap;
  overlaps are free via sync_imports dedupe. Requests persist in
  import_batches via two new nullable columns (range_start/range_end).
- OAuth2 + PKCE on the existing oauth credential kind. Design
  correction from apply: the verifier rides a short-lived httpOnly
  cookie scoped to the callback path — the state param is visible in
  redirect URLs and must never carry it. Manifests opt in via pkce:true.
- Deregistration notifications flip the connection to 'revoked'
  (row kept for audit, imports retained, re-connect prompt shown).
- Framework evolutions, all additive: parseWebhook returns
  WebhookEvent[] (Garmin batches; Wahoo adapted), manifest gains
  configured()/importUrl/pkce, importActivity accepts summary stats
  for FIT-less imports, manager gains markRevoked.
- Env-gated: no GARMIN_CLIENT_ID → provider hidden on
  /settings/connections. Privacy manifest entry (DE+EN). i18n en+de.

Rollout (§6) stays gated on the Garmin Developer Program application
(submitted 2026-06-07). Fixtures are doc-shaped; the staging soak
swaps in recorded payloads if shapes differ.

Gate: typecheck ✓ lint ✓ unit+integration ✓ e2e 70/72 + both known
flakes green isolated ✓ openspec validate ✓

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

infrastructure/docker-compose.staging.yml

@@ -60,6 +60,8 @@ services:
       WAHOO_CLIENT_ID: ""
       WAHOO_CLIENT_SECRET: ""
       WAHOO_WEBHOOK_TOKEN: ""
+      GARMIN_CLIENT_ID: ${GARMIN_CLIENT_ID:-}
+      GARMIN_CLIENT_SECRET: ${GARMIN_CLIENT_SECRET:-}
       DEMO_BOT_ENABLED: ""
       # Federation (social-federation rollout). Enabled by cd-staging.yml
       # for persistent staging (12.2) and for PR previews (12.4 — every