feat(auth): add email-based password reset with MFA + session invalidation

Adds /auth/forgot-password and /auth/reset-password endpoints plus two new
client pages. When SMTP is configured the user receives a branded, i18n-aware
reset email; when it isn't the reset link is logged to the server console in
a clearly-fenced block so self-hosters can relay it manually.

Security properties:
- 256-bit cryptographically-random tokens, only SHA-256 hashes stored in DB
- 60 min expiry, single-use, prior unconsumed tokens auto-invalidated
- Enumeration-safe: /forgot-password always responds {ok:true} with a minimum
  latency pad so timing doesn't leak account existence
- Per-IP rate limit (3/15min on forgot, 5/15min on reset) + per-email throttle
- If the user has MFA enabled, a valid TOTP or backup code is required at
  reset-complete time — a compromised mailbox alone cannot take over a
  2FA-protected account
- New users.password_version column + JWT "pv" claim: bumping it on reset
  invalidates every live session immediately
- Full audit-log coverage (user.password_reset_request/_success/_fail)
- Forgot-page shows a visible hint when SMTP is unconfigured

Migration 115 adds users.password_version and password_reset_tokens
(user_id, token_hash UNIQUE, expires_at, consumed_at, created_ip).

server/src/db/schema.ts

@@ -25,10 +25,23 @@ function createTables(db: Database.Database): void {
       synology_password TEXT,
       synology_sid TEXT,
       must_change_password INTEGER DEFAULT 0,
+      password_version INTEGER NOT NULL DEFAULT 0,
       created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
       updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
     );
 
+    CREATE TABLE IF NOT EXISTS password_reset_tokens (
+      id INTEGER PRIMARY KEY AUTOINCREMENT,
+      user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+      token_hash TEXT NOT NULL UNIQUE,
+      expires_at DATETIME NOT NULL,
+      consumed_at DATETIME,
+      created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+      created_ip TEXT
+    );
+    CREATE INDEX IF NOT EXISTS idx_prt_user ON password_reset_tokens(user_id);
+    CREATE INDEX IF NOT EXISTS idx_prt_hash ON password_reset_tokens(token_hash);
+
     CREATE TABLE IF NOT EXISTS settings (
       id INTEGER PRIMARY KEY AUTOINCREMENT,
       user_id INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,