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.

crates/presentation/src/openapi/mod.rs

@@ -2,6 +2,7 @@ mod auth;
 mod diary;
 mod goals;
 mod import;
+mod insights;
 mod movies;
 mod search;
 mod social;
@@ -46,6 +47,7 @@ fn build() -> utoipa::openapi::OpenApi {
     api.merge(goals::GoalsDoc::openapi());
     api.merge(webhook::WebhookDoc::openapi());
     api.merge(wrapup::WrapUpDoc::openapi());
+    api.merge(insights::InsightsDoc::openapi());
     #[cfg(feature = "federation")]
     api.merge(social::SocialDoc::openapi());
     SecurityAddon.modify(&mut api);