feat: always-on Insights — correlation analysis over viewing habits

Conservative, live insights (ADR-0010) derived from each user's diary:
rating lift by genre (first-time watches only), genre seasonality vs a
uniform 1/12 month baseline, medium weekend-lift, and watch-time rhythm.

- domain: WatchRow model, InsightsQuery port, pure insights_analyzer with
  all honesty thresholds (sample minimums, strength cutoffs, suppressions
  for import noise), unit-tested
- adapters: thin Sqlite/Postgres fetch twins, reusing WrapUp's genre fetch
- application: get_insights use case, InsightsGroup in Deps
- composition/server: wiring through Repositories/DatabaseOutput
- presentation: GET /api/v1/insights handler, typed serde-tagged DTOs,
  openapi doc
- spa: /insights route (shadcn cards), insights feature hook, profile
  entry link, en locale strings
- server test: end-to-end seed sqlite → HTTP → rating lift + rhythm

Also records ADR-0010, defines "Insight" in the glossary, and includes
pre-existing worktree comment-stripping cleanups.

CONTEXT.md

@@ -36,6 +36,10 @@ _Avoid_: Challenge, resolution, target
 A generated summary report of viewing activity over a date range — statistics, trends, highlights, top directors/actors/genres. Can be personal (one user) or global (all users). Generated asynchronously. Shown to users as "Year in Review."
 _Avoid_: Stats page, recap, summary
 
+**Insight**:
+A statement about a user's viewing behavior derived from their Reviews and linked Movie metadata, produced by correlation analysis. Always a comparison — relative to the user's own baseline (their average rating, their genre frequencies, their typical hours) — never a plain ranking or count. "You rate thrillers higher than your average" is an Insight; "thriller is your top genre" is a statistic.
+_Avoid_: Correlation (implementation), fun fact, finding
+
 **User**:
 A registered account with a username, email, and profile (display name, bio, avatar, banner). Can be Standard or Admin.
 _Avoid_: Account, member, profile (as a synonym for the whole User)