Rename sessions table to oauth_sessions for consistency

- Update schema to create oauth_sessions instead of sessions
- Add migration to rename existing sessions table
- Add token_expiry column for OAuth library compatibility

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

db.go

@@ -102,17 +102,18 @@ CREATE TABLE IF NOT EXISTS items (
 -- Indexes will be added as needed based on query patterns
 
 -- OAuth sessions
-CREATE TABLE IF NOT EXISTS sessions (
+CREATE TABLE IF NOT EXISTS oauth_sessions (
 	id TEXT PRIMARY KEY,
 	did TEXT NOT NULL,
 	handle TEXT NOT NULL,
-	access_token TEXT NOT NULL,
+	access_token TEXT,
 	refresh_token TEXT,
 	token_type TEXT NOT NULL DEFAULT 'DPoP',
 	expires_at TIMESTAMP NOT NULL,
 	created_at TIMESTAMP NOT NULL DEFAULT NOW(),
 	dpop_nonce TEXT,
-	dpop_private_jwk TEXT
+	dpop_private_jwk TEXT,
+	token_expiry TIMESTAMP
 );
 
 -- Trigger to normalize feed URLs on insert/update (strips https://, http://, www.)
@@ -215,6 +216,16 @@ func OpenDatabase(connString string) (*DB, error) {
 	pool.Exec(ctx, "CREATE INDEX IF NOT EXISTS idx_domains_host_trgm ON domains USING gin (LOWER(host) gin_trgm_ops)")
 	pool.Exec(ctx, "CREATE INDEX IF NOT EXISTS idx_feeds_domain_host_trgm ON feeds USING gin (LOWER(domain_host) gin_trgm_ops)")
 
+	// Migration: rename old 'sessions' table to 'oauth_sessions'
+	var oldSessionsExists, newSessionsExists bool
+	pool.QueryRow(ctx, "SELECT EXISTS(SELECT 1 FROM information_schema.tables WHERE table_name = 'sessions')").Scan(&oldSessionsExists)
+	pool.QueryRow(ctx, "SELECT EXISTS(SELECT 1 FROM information_schema.tables WHERE table_name = 'oauth_sessions')").Scan(&newSessionsExists)
+	if oldSessionsExists && !newSessionsExists {
+		pool.Exec(ctx, "ALTER TABLE sessions RENAME TO oauth_sessions")
+	}
+	// Add token_expiry column if missing (used by OAuth library)
+	pool.Exec(ctx, "ALTER TABLE oauth_sessions ADD COLUMN IF NOT EXISTS token_expiry TIMESTAMP")
+
 	// Migration: rename feed columns for consistent terminology
 	// last_crawled_at -> last_checked_at (feed_check = checking feeds for new items)
 	// next_crawl_at -> next_check_at