docs: audit mdx docs against multi-engine backend (#484)

* docs: audit mdx docs against multi-engine backend and refresh stale content

Rewrote developer-facing docs that predated the TTSBackend Protocol /
ModelConfig registry refactor (architecture, tts-generation,
model-management, transcription). Updated user-facing docs to reflect all
seven shipped engines (Qwen, Qwen CustomVoice, LuxTTS, Chatterbox,
Chatterbox Turbo, TADA, Kokoro) instead of the outdated "5 engines" claim.

Also fixes:
- Stale app identifier (com.voicebox.app → sh.voicebox.app)
- CUDA backend update flow (now two-archive split, not N-way chunks)
- Whisper model list (removed tiny, added turbo)
- Broken /development/ and /guides/ route links
- Stale just commands and install steps (missing --no-deps chatterbox/tada)
- Removed ASCII art diagrams from README and stories.mdx
- History Generation schema sync with DB model

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

* docs: add DeepWiki badge to README

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

* docs: address PR review feedback

- architecture.mdx: fix backends/ file list (remove nonexistent qwen_backend.py, rename tada_backend.py → hume_backend.py)
- model-management.mdx: Kokoro language count 9 → 8 (matches ModelConfig)
- model-management.mdx: ProgressManager path services/ → utils/
- tts-generation.mdx: ModelConfig example uses field(default_factory=...) — mutable default would raise at runtime
- tts-generation.mdx: "1080p samples" → "on CUDA" (1080p is video, not audio)
- PROJECT_STATUS.md: replace ASCII architecture diagram with prose (matches no-ASCII-art rule)

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

* fix(app): guard against undefined engine in FloatingGenerateBox preset check

form.getValues('engine') returns string | undefined; Set<string>.has()
rejects undefined under strict mode. Added a truthy guard before the
preset lookup.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <[email protected]>

docs/content/docs/overview/remote-mode.mdx

@@ -31,8 +31,16 @@ In Remote Mode, the Voicebox desktop app (running on your local machine) communi
 
     # Install Python dependencies
     pip install -r requirements.txt
+
+    # Engines with incompatible transitive pins — install with --no-deps
+    pip install --no-deps chatterbox-tts
+    pip install --no-deps hume-tada
+
+    # Qwen3-TTS from source
     pip install git+https://github.com/QwenLM/Qwen3-TTS.git
     ```
+
+    Or just run `just setup` from the repo root, which handles all of this.
   </Step>
 
   <Step title="Start the Server">
@@ -135,4 +143,4 @@ Expected performance on various GPUs:
 
 ## Troubleshooting
 
-See the [Troubleshooting Guide](/guides/troubleshooting#remote-mode-issues) for common remote mode issues.
+See the [Troubleshooting Guide](/overview/troubleshooting) for common issues.