feat(dpop): upgrade migration id

migrations/20261012000000_sessions_dpop_jkt.sql

@@ -0,0 +1,34 @@
+-- Bind a session cookie to a browser-held ECDSA keypair (DPoP, RFC 9449).
+--
+-- Each browser session that supports Web Crypto generates a P-256 keypair
+-- with `extractable: false` and stores it in IndexedDB. The public-key JWK
+-- thumbprint (RFC 7638, base64url-encoded SHA-256) is sent with the login
+-- request and stored here. Middleware then requires every subsequent
+-- request on the session to carry a valid DPoP proof signed by the paired
+-- private key. Stealing the cookie alone gets an attacker nothing — the
+-- private key never leaves the browser's crypto subsystem.
+--
+-- Nullable because:
+--   * pre-DPoP sessions created before this feature landed;
+--   * app-password / Nextcloud-client sessions (Basic Auth, no browser,
+--     no Web Crypto) will always have NULL here and are exempted at the
+--     middleware;
+--   * browsers without SubtleCrypto (very rare in 2026) fail the client-
+--     side keypair generation and log in unbound (fail-open per the
+--     `docs/plan/dpop.md` threat model).
+--
+-- Immutable per-session: set at INSERT time, never updated. That's the
+-- point — otherwise an attacker could downgrade a bound session by
+-- clearing the column.
+--
+-- Length is 43 characters for a base64url-encoded SHA-256 (32 bytes ×
+-- 4/3 = 43 chars, no padding). Cap at 64 to leave a little slack in
+-- case we later support larger thumbprints (e.g. SHA-384 for P-384).
+--
+-- No index needed — the column is read alongside the session row by
+-- primary key in the auth middleware, never queried in isolation.
+ALTER TABLE auth.sessions
+    ADD COLUMN IF NOT EXISTS dpop_jkt VARCHAR(64);
+
+COMMENT ON COLUMN auth.sessions.dpop_jkt IS
+    'DPoP JWK thumbprint (RFC 7638) binding this session to a browser-held keypair. NULL for app-password / legacy / unbound sessions.';