Implement full NFC-URL streaming architecture

- rc522: add NDEF URL reading via WUPA+cascade anticoll+SELECT+TLV parse
- AudioPlayer: route http:// URIs to esp_player_http_music_play()
- CacheManager: download URLs async to /sdcard/cache/{hash}.{ext}
- TagPlayerControl: NDEF URL → cache-or-stream; fallback to UID local mapping
- RFIDInterface: wire ndef_callback, expose combined uid+url callback
- WebInterface: add /api/info, /api/storage, /api/playback, /api/bluetooth
- BluetoothInterface: stub for A2DP speaker mode
- Networking: WiFi connect with 30s timeout instead of blocking forever
- main.cpp: re-enable WiFi + web server, fix init order, add CacheManager
- www/: full SPA — playback controls, device info, storage, BT pairing
- .gitmodules: switch rc522 submodule URL to HTTPS

https://claude.ai/code/session_01MhAnh68DPNnTjcKqjNYDmk

device/main/CacheManager.hpp

@@ -0,0 +1,46 @@
+#pragma once
+
+#include <string>
+#include <vector>
+#include <functional>
+
+struct CacheEntry {
+    std::string key;     /* hex hash of the URL */
+    std::string url;
+    std::string path;    /* full SD card path */
+    size_t      size;    /* file size in bytes, 0 if unknown */
+};
+
+class CacheManager {
+public:
+    CacheManager();
+
+    /* Returns the SD-card path for url if cached, or empty string if not. */
+    std::string getCachedPath(const std::string& url) const;
+
+    /* Enqueue an async FreeRTOS task that downloads url and caches it.
+     * onComplete is called (from the download task) when done or on error. */
+    void downloadAsync(const std::string& url, std::function<void(bool success)> onComplete = nullptr);
+
+    /* List all cached entries. */
+    std::vector<CacheEntry> listEntries() const;
+
+    /* Delete a single cache entry by key (hex hash). Returns true if deleted. */
+    bool deleteEntry(const std::string& key);
+
+    /* Delete the entire cache directory. */
+    void deleteAll();
+
+    /* Total bytes used by cache. */
+    size_t totalBytes() const;
+
+private:
+    static constexpr const char* CACHE_DIR = "/sdcard/cache";
+
+    std::string urlToKey(const std::string& url) const;
+    std::string urlExtension(const std::string& url) const;
+    std::string keyToPath(const std::string& key, const std::string& ext) const;
+    std::string findFileByKey(const std::string& key) const;
+
+    static void downloadTask(void* arg);
+};