fix(audit-2): integration regressions + data-integrity from second-pass review

Two reviewer agents did a second-pass deep audit of the 21-commit
refactor. Eight findings; four fixed here (one was deferred with a
schema comment, three were 🟡 nice-to-haves left for follow-up).

Integration regressions (🟠 high):
- Outbound webhook `interest.berth_linked` now fires from the new
  junction-add handler. Was emitting a socket-only event, leaving
  external integrations silent post-refactor.
- Two new webhook events `interest.berth_unlinked` and
  `interest.berth_link_updated` added to WEBHOOK_EVENTS +
  INTERNAL_TO_WEBHOOK_MAP. PATCH and DELETE handlers now dispatch them
  alongside the existing socket emits — lifecycle parity restored.
- BerthInterestPulse adds useRealtimeInvalidation for berth-link
  events. The query key was berth-scoped while the linked-berths
  dialog invalidates interest-scoped keys (no prefix match), so the
  pulse went stale. Bridges via the realtime hook now.

Recommender semantic fix (🟠 medium-high):
- aggregates CTE: active_interest_count now filters on
  `ib.is_specific_interest = true`, matching the public-map "Under
  Offer" derivation. EOI-bundle-only links no longer demote a berth
  to Tier C for other reps. Smoke test confirms previously-all-Tier-C
  results now correctly classify as Tier A.
- Same CTE: `total_interest_count` uses COUNT(ib.berth_id) instead of
  COUNT(*) so a berth with no junction rows reports 0 (not 1 from
  the LEFT JOIN's NULL-right-side row). Prevents heat over-counting.

Data integrity (🟠):
- AcroForm tier rejects negative numerics in coerceFieldValue (was
  letting through `length_ft="-50"` which would poison the
  recommender feasibility filter on apply).
- FilesystemBackend.resolveHmacSecret throws in production when
  storage_proxy_hmac_secret_encrypted is null. Dev still derives from
  BETTER_AUTH_SECRET for ergonomics; prod must explicitly configure.
- Documented the circular FK between berths.current_pdf_version_id
  and berth_pdf_versions.id. Drizzle's `.references()` can't express
  the cycle so the schema column is plain text + a comment; the FK
  is authoritatively maintained by migration 0030.

Tests still 1163/1163. tsc clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/db/schema/berths.ts

@@ -92,6 +92,17 @@ export const berths = pgTable(
   ],
 );
 
+// Note: `berths.current_pdf_version_id` has an `ON DELETE SET NULL` FK to
+// `berth_pdf_versions.id` installed by migration 0030. The column is left
+// without a `.references()` / `foreignKey()` declaration in the Drizzle
+// schema because the two tables form a circular FK (berth_pdf_versions →
+// berths), and Drizzle's relation inference doesn't tolerate the cycle
+// when both sides are declared via column-level `.references()`. The
+// migration chain authoritatively maintains the constraint; a fresh
+// `db:push` against an empty DB would skip the FK and require a follow-up
+// generated migration to add it back. This is acceptable because we
+// always apply migrations in order in dev/CI/prod.
+
 export const berthMapData = pgTable(
   'berth_map_data',
   {