release: v0.50.102–v0.50.108 batch (code blocks, utf-8, image URLs, deletion warning, PermissionError, Docker docs, kimi-k2.5) (#755)

## Batch release: v0.50.102 – v0.50.108

Seven self-built PRs reviewed and approved by @nesquena, now consolidated into a single release branch.

### Included fixes

| Version | PR | What it fixes |
|---|---|---|
| v0.50.102 | #746 | Code blocks lose newlines when not preceded by blank line (fixes #745) |
| v0.50.103 | #743 | `encoding='utf-8'` on `write_text()` in `api/profiles.py` — Windows `.env` detection (fixes #741) |
| v0.50.104 | #735 | Agent `MEDIA:localhost:*` image URLs rewritten to `document.baseURI` — remote users get working images (fixes #642) |
| v0.50.105 | #736 | Profile deletion warning strengthened: "permanently deleted, cannot be undone" across all 6 locales (fixes #637) |
| v0.50.106 | #738 | Catch `PermissionError` in `_signing_key()` — three-container Docker UID mismatch no longer crashes all HTTP requests |
| v0.50.107 | #737 | Docs: three-container UID/GID alignment guide in README + `HERMES_UID`/`HERMES_GID` forwarded in compose (fixes #645) |
| v0.50.108 | #742 | Add `kimi-k2.5` to Kimi/Moonshot provider model list (fixes #740) |

### Testing
- **pytest**: 1510 passed, 1 warning (1 pre-existing unrelated failure excluded)
- **QA harness**: 20/20 passed (`~/WebUI/scripts/run-browser-tests.sh`)
- **Browser**: layout, slash autocomplete width, edit button, image URL rewrite, profile deletion dialog all verified

All PRs reviewed and approved by @nesquena. Ready to merge and tag **v0.50.108**.

api/auth.py

@@ -51,13 +51,13 @@ def _record_login_attempt(ip: str) -> None:
 def _signing_key():
     """Return a random signing key, generating and persisting one on first call."""
     key_file = STATE_DIR / '.signing_key'
-    if key_file.exists():
-        try:
+    try:
+        if key_file.exists():
             raw = key_file.read_bytes()
             if len(raw) >= 32:
                 return raw[:32]
-        except Exception:
-            logger.debug("Failed to read signing key from file, generating new key")
+    except Exception:
+        logger.debug("Failed to read or access signing key file, using in-memory key")
     # Generate a new random key
     key = secrets.token_bytes(32)
     try: