feat(diagnostics): persistent redacted logging and an exportable bundle

The app forgot everything it did the moment it exited. The Rust half
logged through env_logger to stdout only -- invisible to anyone who
launched from a desktop icon, and on Android worse than that: stdout is
not logcat, so the backend produced no visible output at all on the
platform carrying this project's hardest bugs. The autoplay deadlock,
the truncated-stream restart and the background-audio stall were all
diagnosed by talking a user through `adb logcat`, because there was no
other way to see anything. A panic left nothing behind at all.

Logs now go to a size-capped rotating file, to logcat on Android, and to
the webview console in dev. A panic is recorded with its backtrace before
the process dies. The frontend's messages are forwarded into the same
file, so one timeline holds both halves of the app in order -- which is
what makes a race between them legible after the fact, and races between
them are the expensive bug class here.

Redaction runs in the log FORMATTER, not at export time. A credential
sitting in a file on the device is already a disclosure; stripping it on
the way out would be too late. The exporter redacts a second time to
cover files written by builds that predate this. api_key, X-Emby-Token,
Authorization, "AccessToken" and Token="..." all reduce to [REDACTED],
while host, item ids and filenames are deliberately kept -- a log scrubbed
of those is one nobody can debug anything from. Server URLs keep scheme
and host and drop any embedded user:pass@.

Two things the tests caught that review would not have:

  - redact_headers recursed on its own output. The replacement keeps the
    header NAME, so the next call matched the same header forever; the
    test died with a stack overflow. It is a forward scan now.
  - The frontend forwarder used `void plugin.error(...)`. `void` discards
    a promise's value but not its rejection, so in any webview without
    IPC -- a unit test, SSR, a browser preview -- every log line became an
    unhandled rejection. 20 of them showed up the first time coverage
    ran. Each call now attaches a catch.

Only info and above cross the IPC boundary: debug is per-tick player
state and forwarding it would be thousands of calls a minute for output
nobody reads. A failing forwarder never propagates and never prevents the
console write.

Nothing is transmitted anywhere. The export writes a zip and reports its
path; the user attaches it themselves, which is also what keeps this from
becoming telemetry. An Android share intent is explicitly out of scope --
it is Kotlin work that belongs with the other native code.

The panic hook chains to the previous hook rather than replacing it,
because utils/lock.rs installs a silencing hook around tests that provoke
poisoned locks on purpose.

Spec in docs/specs/diagnostics-and-logging.md; UR-078 / DR-218 / UT-209.

Verified: 1079 frontend tests and the coverage gate, 759 Rust tests,
clippy -D warnings, svelte-check 0 errors, and cargo check for
aarch64-linux-android.

bun.lock

@@ -6,6 +6,7 @@
       "name": "jellytau",
       "dependencies": {
         "@tauri-apps/api": "^2",
+        "@tauri-apps/plugin-log": "^2.9.0",
         "@tauri-apps/plugin-opener": "^2",
         "@tauri-apps/plugin-os": "^2.3.2",
         "@tauri-apps/plugin-process": "^2.3.1",
@@ -280,6 +281,8 @@
 
     "@tauri-apps/cli-win32-x64-msvc": ["@tauri-apps/cli-win32-x64-msvc@2.9.6", "", { "os": "win32", "cpu": "x64" }, "sha512-ldWuWSSkWbKOPjQMJoYVj9wLHcOniv7diyI5UAJ4XsBdtaFB0pKHQsqw/ItUma0VXGC7vB4E9fZjivmxur60aw=="],
 
+    "@tauri-apps/plugin-log": ["@tauri-apps/plugin-log@2.9.0", "", { "dependencies": { "@tauri-apps/api": "^2.11.0" } }, "sha512-Ql8okrnsguk0eDq1GvRfttFV5KaeW/7vcao6bdbkXCRJ1+2sWE15ZJvJVEKVANrOKy1mRngqC3IFIAP+wP5qSw=="],
+
     "@tauri-apps/plugin-opener": ["@tauri-apps/plugin-opener@2.5.2", "", { "dependencies": { "@tauri-apps/api": "^2.8.0" } }, "sha512-ei/yRRoCklWHImwpCcDK3VhNXx+QXM9793aQ64YxpqVF0BDuuIlXhZgiAkc15wnPVav+IbkYhmDJIv5R326Mew=="],
 
     "@tauri-apps/plugin-os": ["@tauri-apps/plugin-os@2.3.2", "", { "dependencies": { "@tauri-apps/api": "^2.8.0" } }, "sha512-n+nXWeuSeF9wcEsSPmRnBEGrRgOy6jjkSU+UVCOV8YUGKb2erhDOxis7IqRXiRVHhY8XMKks00BJ0OAdkpf6+A=="],
@@ -758,6 +761,8 @@
 
     "@tailwindcss/oxide-wasm32-wasi/tslib": ["tslib@2.8.1", "", { "bundled": true }, "sha512-oJFu94HQb+KVduSUQL7wnpmqnfmLsOA/nAh6b6EH0wCEoK0/mPeXU6c3wKDV83MkOuHPRHtSXKKU99IBazS/2w=="],
 
+    "@tauri-apps/plugin-log/@tauri-apps/api": ["@tauri-apps/api@2.11.1", "", {}, "sha512-M2FPuYND2m+wh5hfW9ZpSdxMPdEJovPBWwoHJmwUpysTYNHaOkVFN419m/K0LIgjb/7KU2vBgsUepJWugQCvAA=="],
+
     "@tauri-apps/plugin-updater/@tauri-apps/api": ["@tauri-apps/api@2.11.1", "", {}, "sha512-M2FPuYND2m+wh5hfW9ZpSdxMPdEJovPBWwoHJmwUpysTYNHaOkVFN419m/K0LIgjb/7KU2vBgsUepJWugQCvAA=="],
 
     "@testing-library/dom/aria-query": ["aria-query@5.3.0", "", { "dependencies": { "dequal": "^2.0.3" } }, "sha512-b0P0sZPKtyu8HkeRAfCq0IfURZK+SuwMjY1UXGBU27wpAiTwQAIlq56IbIO+ytk/JjS1fMR14ee5WBBfKi5J6A=="],