"We Met" scan experience — capture connections on scan

Experience #1 from the scan-experiences brief: when someone scans a card and
shares back, capture the meeting (with coarse geo + time) so the owner gets a
"People I met" list.

Backend (cardclaws-backend):
- migration 0006_connections.sql: connections table (card_id, owner_id, name,
  email, note, country, city, met_at). Raw IP never stored — only resolved geo.
- POST /v1/profile/:handle/connect (public, rate-limited 5/min): captures the
  connection with geo, emails the owner best-effort.
- GET /v1/cards/:id/connections (owner-only): the People-I-met list.
- ConnectionRow model + connections queries (insert, list_by_card);
  profile_service::submit_connection; card_service::list_connections.
- 2 tests (capture→owner-list + validation, owner-only); gate green (118 tests).
- Verified live end-to-end.

Web (cardclaws-profile):
- [handle].astro: a "We met?" share-back form posting to /connect; astro check
  clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

cardclaws-backend/crates/cardclaws-db/migrations/0006_connections.sql

@@ -0,0 +1,17 @@
+-- "We Met" scan experience (PRD §21 Phase 5): when someone scans a card and
+-- shares back, we capture the meeting (with coarse geo + time) so the owner gets
+-- a "People I met" list. Raw IP is never stored — only the resolved country/city.
+CREATE TABLE connections (
+    id          UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    card_id     UUID NOT NULL REFERENCES cards(id) ON DELETE CASCADE,
+    owner_id    UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    name        TEXT NOT NULL,
+    email       TEXT,
+    note        TEXT,
+    country     TEXT,
+    city        TEXT,
+    met_at      TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX idx_connections_card ON connections(card_id, met_at DESC);
+CREATE INDEX idx_connections_owner ON connections(owner_id, met_at DESC);