Add social features and harden beta release

db/migrations/07_friendships_and_privacy.sql

@@ -0,0 +1,18 @@
+ALTER TABLE users
+ADD COLUMN IF NOT EXISTS profile_visibility VARCHAR(20) NOT NULL DEFAULT 'public'
+CHECK (profile_visibility IN ('public', 'friends'));
+
+CREATE TABLE IF NOT EXISTS friendships (
+    id SERIAL PRIMARY KEY,
+    requester_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    addressee_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    status VARCHAR(20) NOT NULL DEFAULT 'pending'
+        CHECK (status IN ('pending', 'accepted')),
+    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    CHECK (requester_id <> addressee_id),
+    UNIQUE (requester_id, addressee_id)
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS idx_friendships_pair
+ON friendships (LEAST(requester_id, addressee_id), GREATEST(requester_id, addressee_id));