Upload date in UI; extract HTML_UI; Twitch clips mode; DB connection pool

Four nice-to-have items, plus surfacing the upload date in both UIs
since the user explicitly asked.

Upload date display
- Desktop: card meta row now includes a `YYYY-MM-DD` cell between the
  ID and the duration; detail panel header shows it as `📅 YYYY-MM-DD`.
- Web: video player modal title gains a date+duration subline so the
  viewer has context without opening the metadata pane (card meta
  already shows the date).
- New `format_upload_date()` helper on the desktop side; the web side
  reuses the existing `fmtDate()` JS.

Extract HTML_UI to include_str!
- `LOGIN_HTML` and `HTML_UI` moved out of `src/web.rs` into
  `src/web_ui/login.html` and `src/web_ui/index.html`. The Rust file
  drops from 2915 lines to 1806; editors now syntax-highlight the
  HTML/CSS/JS, and UI diffs no longer overwhelm the Rust diff view.
- `include_str!` bakes them into the binary at compile time, so there
  is no runtime fs lookup and no extra deploy artifacts.

Twitch clips-only mode
- `classify_twitch` now recognises `twitch.tv/<user>/clips` as a
  Channel URL (was Unknown), so yt-dlp's TwitchClips extractor is
  reachable from our normal download pipeline.
- Both UIs gain a "Clips only" toggle visible only when the URL is
  a Twitch channel (not a specific VOD/clip). On submit, the URL is
  rewritten to `twitch.tv/<user>/clips` before dispatch.
- 1 new platform test covers the clips-listing classification.

DB connection pool (r2d2_sqlite)
- `Database` now wraps an `r2d2`-managed SQLite pool. File-backed
  databases get up to 4 connections; the in-memory fallback is capped
  at 1 (since each in-memory connection is a fresh empty DB by default
  in SQLite).
- `WebState.db` drops its outer `Mutex` — concurrent handlers each
  check out their own connection from the pool. Static-file fetches
  through `/files/` no longer serialize on the watched/positions/
  password lookups that the auth middleware performs.
- Pool init failures are converted to `rusqlite::Error` so the
  existing `Result<T>` return types still work.

47 unit tests pass.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Cargo.lock

@@ -192,7 +192,7 @@ checksum = "3c3610892ee6e0cbce8ae2700349fcf8f98adb0dbfbee85aec3c9179d29cc072"
 dependencies = [
  "base64ct",
  "blake2",
- "cpufeatures",
+ "cpufeatures 0.2.17",
  "password-hash",
 ]
 
@@ -268,6 +268,18 @@ dependencies = [
  "pin-project-lite",
 ]
 
+[[package]]
+name = "async-compression"
+version = "0.4.42"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e79b3f8a79cccc2898f31920fc69f304859b3bd567490f75ebf51ae1c792a9ac"
+dependencies = [
+ "compression-codecs",
+ "compression-core",
+ "pin-project-lite",
+ "tokio",
+]
+
 [[package]]
 name = "async-executor"
 version = "1.14.0"
@@ -732,6 +744,17 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "chacha20"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6f8d983286843e49675a4b7a2d174efe136dc93a18d69130dd18198a6c167601"
+dependencies = [
+ "cfg-if",
+ "cpufeatures 0.3.0",
+ "rand_core 0.10.1",
+]
+
 [[package]]
 name = "clipboard-win"
 version = "5.4.1"
@@ -792,6 +815,23 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "compression-codecs"
+version = "0.4.38"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ce2548391e9c1929c21bf6aa2680af86fe4c1b33e6cea9ac1cfeec0bd11218cf"
+dependencies = [
+ "compression-core",
+ "flate2",
+ "memchr",
+]
+
+[[package]]
+name = "compression-core"
+version = "0.4.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cc14f565cf027a105f7a44ccf9e5b424348421a1d8952a8fc9d499d313107789"
+
 [[package]]
 name = "concurrent-queue"
 version = "2.5.0"
@@ -860,6 +900,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "cpufeatures"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b2a41393f66f16b0823bb79094d54ac5fbd34ab292ddafb9a0456ac9f87d201"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "crc32fast"
 version = "1.5.0"
@@ -1395,6 +1444,7 @@ dependencies = [
  "cfg-if",
  "libc",
  "r-efi 6.0.0",
+ "rand_core 0.10.1",
  "wasip2",
  "wasip3",
 ]
@@ -2873,6 +2923,28 @@ version = "6.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f8dcc9c7d52a811697d2151c701e0d08956f92b0e24136cf4cf27b57a6a0d9bf"
 
+[[package]]
+name = "r2d2"
+version = "0.8.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "51de85fb3fb6524929c8a2eb85e6b6d363de4e8c48f9e2c2eac4944abc181c93"
+dependencies = [
+ "log",
+ "parking_lot",
+ "scheduled-thread-pool",
+]
+
+[[package]]
+name = "r2d2_sqlite"
+version = "0.24.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a982edf65c129796dba72f8775b292ef482b40d035e827a9825b3bc07ccc5f2"
+dependencies = [
+ "r2d2",
+ "rusqlite",
+ "uuid",
+]
+
 [[package]]
 name = "rand"
 version = "0.8.6"
@@ -2894,6 +2966,17 @@ dependencies = [
  "rand_core 0.9.5",
 ]
 
+[[package]]
+name = "rand"
+version = "0.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d2e8e8bcc7961af1fdac401278c6a831614941f6164ee3bf4ce61b7edb162207"
+dependencies = [
+ "chacha20",
+ "getrandom 0.4.2",
+ "rand_core 0.10.1",
+]
+
 [[package]]
 name = "rand_chacha"
 version = "0.3.1"
@@ -2932,6 +3015,12 @@ dependencies = [
  "getrandom 0.3.4",
 ]
 
+[[package]]
+name = "rand_core"
+version = "0.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "63b8176103e19a2643978565ca18b50549f6101881c443590420e4dc998a3c69"
+
 [[package]]
 name = "raw-window-handle"
 version = "0.6.2"
@@ -3077,6 +3166,15 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "scheduled-thread-pool"
+version = "0.2.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3cbc66816425a074528352f5789333ecff06ca41b36b0b0efdfbb29edc391a19"
+dependencies = [
+ "parking_lot",
+]
+
 [[package]]
 name = "scoped-tls"
 version = "1.0.1"
@@ -3201,7 +3299,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e3bf829a2d51ab4a5ddf1352d8470c140cadc8301b2ae1789db023f01cedd6ba"
 dependencies = [
  "cfg-if",
- "cpufeatures",
+ "cpufeatures 0.2.17",
  "digest",
 ]
 
@@ -3685,8 +3783,10 @@ version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1e9cd434a998747dd2c4276bc96ee2e0c7a2eadf3cae88e52be55a05fa9053f5"
 dependencies = [
+ "async-compression",
  "bitflags 2.11.1",
  "bytes",
+ "futures-core",
  "futures-util",
  "http",
  "http-body",
@@ -3841,7 +3941,9 @@ version = "1.23.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ddd74a9687298c6858e9b88ec8935ec45d22e8fd5e6394fa1bd4e99a87789c76"
 dependencies = [
+ "getrandom 0.4.2",
  "js-sys",
+ "rand 0.10.1",
  "serde_core",
  "wasm-bindgen",
 ]
@@ -4939,6 +5041,8 @@ dependencies = [
  "eframe",
  "image",
  "notify-rust",
+ "r2d2",
+ "r2d2_sqlite",
  "rand 0.8.6",
  "rfd",
  "rusqlite",