WebSocket job progress + mobile-responsive web UI

WebSocket progress
- New `/ws/progress` route using axum 0.7's `ws` feature. Upgrades to
  a WebSocket that streams the same `ProgressResponse` payload as the
  HTTP polling endpoint, pushed instantly whenever a job moves.
- `WebState.progress_tx` is a `tokio::sync::broadcast::Sender<String>`
  (capacity 16, lossy — Lagged subscribers resync on the next tick).
- A background tokio task ticks every 500 ms while any download is
  running or queued, every 5 s when idle. Skips the JSON encode when
  no subscribers are listening, so a single-user install pays zero
  CPU for the broadcast when the browser tab is closed.
- JS replaces the per-interval HTTP poll with a WebSocket connection.
  The polling path stays as fallback for mobile carriers / reverse
  proxies that strip WS — when the socket closes or fails to open,
  schedulePoll() resumes immediately and a reconnect attempt fires
  after 5 s.
- Initial snapshot is sent right after subscribe so the UI is live
  before the next tick.

Mobile-responsive web UI
- Existing `@media(max-width:640px)` block tightened:
  - Hide the H1, AGPL footer notice, sort dropdown, and library-size
    counter — they don't fit and aren't actionable.
  - Header buttons get min 34×34 hit targets (Apple HIG / Material).
  - `.card-foot` wraps and grows to 34×34 buttons so the five action
    icons (play / watched / favourite / bookmark / waiting) stay
    tappable instead of cramming into thumb-unfriendly 22 px chips.
  - Modals go full-screen (no 10 px page-margin) so the iPhone safe
    area doesn't crop content.
  - Footer (URL bar + download button) wraps onto two rows so neither
    squeezes the other off-screen.
  - Bulk-actions toolbar wraps and gets bigger buttons.
  - Per-job stdout preview hides on small screens.
- New `@media(max-width:380px)` collapses the grid to single column
  for very narrow phones.

55 unit tests still pass.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Cargo.lock

@@ -470,6 +470,7 @@ dependencies = [
  "async-trait",
  "axum-core",
  "axum-macros",
+ "base64",
  "bytes",
  "futures-util",
  "http",
@@ -488,8 +489,10 @@ dependencies = [
  "serde_json",
  "serde_path_to_error",
  "serde_urlencoded",
+ "sha1",
  "sync_wrapper",
  "tokio",
+ "tokio-tungstenite",
  "tower",
  "tower-layer",
  "tower-service",
@@ -528,6 +531,12 @@ dependencies = [
  "syn 2.0.117",
 ]
 
+[[package]]
+name = "base64"
+version = "0.22.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72b3254f16251a8381aa12e40e3c4d2f0199f8c6508fbecb9d91f575e0fbb8c6"
+
 [[package]]
 name = "base64ct"
 version = "1.8.3"
@@ -642,6 +651,12 @@ dependencies = [
  "syn 2.0.117",
 ]
 
+[[package]]
+name = "byteorder"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1fd0f2584146f6f2ef48085050886acf353beff7305ebd1ae69500e27c67f64b"
+
 [[package]]
 name = "byteorder-lite"
 version = "0.1.0"
@@ -940,6 +955,12 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f27ae1dd37df86211c42e150270f82743308803d90a6f6e6651cd730d5e1732f"
 
+[[package]]
+name = "data-encoding"
+version = "2.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a4ae5f15dda3c708c0ade84bfee31ccab44a3da4f88015ed22f63732abe300c8"
+
 [[package]]
 name = "deranged"
 version = "0.5.8"
@@ -3684,6 +3705,18 @@ dependencies = [
  "tokio",
 ]
 
+[[package]]
+name = "tokio-tungstenite"
+version = "0.24.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "edc5f74e248dc973e0dbb7b74c7e0d6fcc301c694ff50049504004ef4d0cdcd9"
+dependencies = [
+ "futures-util",
+ "log",
+ "tokio",
+ "tungstenite",
+]
+
 [[package]]
 name = "tokio-util"
 version = "0.7.18"
@@ -3854,6 +3887,24 @@ version = "0.25.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d2df906b07856748fa3f6e0ad0cbaa047052d4a7dd609e231c4f72cee8c36f31"
 
+[[package]]
+name = "tungstenite"
+version = "0.24.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "18e5b8366ee7a95b16d32197d0b2604b43a0be89dc5fac9f8e96ccafbaedda8a"
+dependencies = [
+ "byteorder",
+ "bytes",
+ "data-encoding",
+ "http",
+ "httparse",
+ "log",
+ "rand 0.8.6",
+ "sha1",
+ "thiserror 1.0.69",
+ "utf-8",
+]
+
 [[package]]
 name = "type-map"
 version = "0.5.1"
@@ -3929,6 +3980,12 @@ version = "2.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "daf8dba3b7eb870caf1ddeed7bc9d2a049f3cfdfae7cb521b087cc33ae4c49da"
 
+[[package]]
+name = "utf-8"
+version = "0.7.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09cc8ee72d2a9becf2f2febe0205bbed8fc6615b7cb429ad062dc7b7ddd036a9"
+
 [[package]]
 name = "utf8_iter"
 version = "1.0.4"