Initial commit: JARVIS AI dashboard v2.3

- 4-tier chat: HA control → Ollama → Groq → Claude
- Push-based agent system with heartbeat/metrics
- Network monitoring, alerts, Proxmox, Home Assistant
- Windows + Linux agent installers
- Stats cache cron, facts collector, KB engine

api/lib/db.php

@@ -0,0 +1,40 @@
+<?php
+class JarvisDB {
+    private static ?PDO $pdo = null;
+
+    public static function get(): PDO {
+        if (self::$pdo === null) {
+            self::$pdo = new PDO(
+                'mysql:host=' . DB_HOST . ';dbname=' . DB_NAME . ';charset=utf8mb4',
+                DB_USER, DB_PASS,
+                [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
+                 PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
+                 PDO::ATTR_EMULATE_PREPARES => false]
+            );
+        }
+        return self::$pdo;
+    }
+
+    public static function query(string $sql, array $params = []): array {
+        $stmt = self::get()->prepare($sql);
+        $stmt->execute($params);
+        return $stmt->fetchAll();
+    }
+
+    public static function execute(string $sql, array $params = []): int {
+        $stmt = self::get()->prepare($sql);
+        $stmt->execute($params);
+        return $stmt->rowCount();
+    }
+
+    public static function single(string $sql, array $params = []): ?array {
+        $rows = self::query($sql, $params);
+        return $rows[0] ?? null;
+    }
+
+    public static function insert(string $sql, array $params = []): int {
+        $stmt = self::get()->prepare($sql);
+        $stmt->execute($params);
+        return (int)self::get()->lastInsertId();
+    }
+}