Optimize server startup speed, client update caching, and HTTP 304 conditional downloads

src/storage_engine.py

@@ -193,19 +193,24 @@ class StorageEngine:
                 )
             """)
 
+            def _ensure_columns(tbl: str, cols: List[Tuple[str, str]]):
+                try:
+                    existing = {row[1] for row in conn.execute(f"PRAGMA table_info({tbl})").fetchall()}
+                    for col, col_def in cols:
+                        if col not in existing:
+                            conn.execute(f"ALTER TABLE {tbl} ADD COLUMN {col} {col_def}")
+                except Exception:
+                    pass
+
             # Migrations for license_config
-            for col, col_def in [
+            _ensure_columns("license_config", [
                 ("license_id", "TEXT"),
                 ("license_server_url", "TEXT"),
                 ("issued_at", "TEXT"),
                 ("expires_at", "TEXT"),
                 ("license_status", "TEXT DEFAULT 'unlicensed'"),
                 ("features", "TEXT DEFAULT '[]'")
-            ]:
-                try:
-                    conn.execute(f"ALTER TABLE license_config ADD COLUMN {col} {col_def}")
-                except sqlite3.OperationalError:
-                    pass
+            ])
 
             # 4. Clients Table
             conn.execute("""
@@ -221,7 +226,7 @@ class StorageEngine:
             """)
 
             # Migrations for clients table
-            for col, col_def in [
+            _ensure_columns("clients", [
                 ("metrics_json", "TEXT DEFAULT '{}'"),
                 ("cpu_percent", "REAL DEFAULT 0.0"),
                 ("memory_percent", "REAL DEFAULT 0.0"),
@@ -229,11 +234,7 @@ class StorageEngine:
                 ("client_version", "TEXT DEFAULT ''"),
                 ("update_status", "TEXT DEFAULT 'up_to_date'"),
                 ("last_update_check", "TEXT")
-            ]:
-                try:
-                    conn.execute(f"ALTER TABLE clients ADD COLUMN {col} {col_def}")
-                except sqlite3.OperationalError:
-                    pass
+            ])
 
             # 5. Users Table
             conn.execute("""
@@ -249,14 +250,10 @@ class StorageEngine:
             """)
 
             # Migrations for users table (2FA)
-            for col, col_def in [
+            _ensure_columns("users", [
                 ("totp_secret", "TEXT"),
                 ("totp_enabled", "INTEGER DEFAULT 0")
-            ]:
-                try:
-                    conn.execute(f"ALTER TABLE users ADD COLUMN {col} {col_def}")
-                except sqlite3.OperationalError:
-                    pass
+            ])
 
             # Ensure default admin user exists
             c = conn.cursor()