fix: native video fullscreen, window dragging, quality picker, spinner

Enable WKWebView's elementFullscreenEnabled at startup. It is off by
default in a Tauri window, which is why the native player had no
full-screen button and why right-click 'Enter Full Screen' did nothing.
With it on, WebKit's own control appears on the video and gives the real
system fullscreen player, so the app-level workaround is gone.

Restore window dragging: data-tauri-drag-region needs
core:window:allow-start-dragging, which was missing, leaving the
title-bar strip inert.

Download quality is now a resolution picker (best/2160/1440/1080/720/
480) instead of a two-way toggle; every selector still pins AAC audio
because Opus in MP4 is silent in WebKit.

Tile titles truncate to a single line so rows stay uniform, and the
player shows a spinner while the video buffers, not just while the
stream URL resolves.

src-tauri/Cargo.lock

@@ -1141,6 +1141,7 @@ dependencies = [
  "chrono",
  "csv",
  "futures",
+ "objc2-web-kit",
  "quick-xml 0.42.0",
  "reqwest",
  "rusqlite",
@@ -2597,6 +2598,16 @@ dependencies = [
  "objc2-core-foundation",
 ]
 
+[[package]]
+name = "objc2-javascript-core"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2a1e6550c4caed348956ce3370c9ffeca70bb1dbed4fa96112e7c6170e074586"
+dependencies = [
+ "objc2",
+ "objc2-core-foundation",
+]
+
 [[package]]
 name = "objc2-quartz-core"
 version = "0.3.2"
@@ -2609,6 +2620,17 @@ dependencies = [
  "objc2-foundation",
 ]
 
+[[package]]
+name = "objc2-security"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "709fe137109bd1e8b5a99390f77a7d8b2961dafc1a1c5db8f2e60329ad6d895a"
+dependencies = [
+ "bitflags 2.13.1",
+ "objc2",
+ "objc2-core-foundation",
+]
+
 [[package]]
 name = "objc2-ui-kit"
 version = "0.3.2"
@@ -2652,6 +2674,8 @@ dependencies = [
  "objc2-app-kit",
  "objc2-core-foundation",
  "objc2-foundation",
+ "objc2-javascript-core",
+ "objc2-security",
 ]
 
 [[package]]