feat: add Admin Panel with JWT auth, DB settings, and integration management

Complete admin backend with login, where all integrations (weather, news,
Home Assistant, Vikunja, Unraid, MQTT) can be configured via web UI instead
of ENV variables. Two-layer config: ENV seeds DB on first start, then DB
is source of truth. Auto-migration system on startup.

Backend: db.py shared pool, auth.py JWT, settings_service CRUD, seed_service,
admin router (protected), test_connections per integration, config.py rewrite.

Frontend: react-router v6, login page, admin layout with sidebar, 8 settings
pages (General, Weather, News, HA, Vikunja, Unraid, MQTT, ChangePassword),
shared IntegrationForm + TestButton components.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/migrations/runner.py

@@ -0,0 +1,58 @@
+"""Auto-migration runner. Applies pending SQL migrations on startup."""
+
+from __future__ import annotations
+
+import logging
+from pathlib import Path
+
+import asyncpg
+
+logger = logging.getLogger(__name__)
+
+MIGRATIONS_DIR = Path(__file__).parent
+
+
+async def run_migrations(pool: asyncpg.Pool) -> None:
+    """Check schema_version and apply any pending .sql migration files."""
+    async with pool.acquire() as conn:
+        # Ensure the version-tracking table exists
+        await conn.execute("""
+            CREATE TABLE IF NOT EXISTS schema_version (
+                version     INTEGER PRIMARY KEY,
+                applied_at  TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+                description TEXT NOT NULL DEFAULT ''
+            )
+        """)
+
+        row = await conn.fetchrow(
+            "SELECT COALESCE(MAX(version), 0) AS v FROM schema_version"
+        )
+        current_version: int = row["v"]
+        logger.info("Current schema version: %d", current_version)
+
+        # Discover and sort SQL files by their numeric prefix
+        sql_files = sorted(
+            MIGRATIONS_DIR.glob("[0-9]*.sql"),
+            key=lambda p: int(p.stem.split("_")[0]),
+        )
+
+        applied = 0
+        for sql_file in sql_files:
+            version = int(sql_file.stem.split("_")[0])
+            if version <= current_version:
+                continue
+
+            logger.info("Applying migration %03d: %s", version, sql_file.name)
+            sql = sql_file.read_text(encoding="utf-8")
+
+            # Execute the entire migration in a transaction
+            async with conn.transaction():
+                await conn.execute(sql)
+
+            logger.info("Migration %03d applied successfully", version)
+            applied += 1
+
+        if applied == 0:
+            logger.info("No pending migrations")
+        else:
+            logger.info("Applied %d migration(s)", applied)