refactor: comprehensive code review fixes across 31 files

Addresses all critical, high, medium, and low issues from full codebase
review. 494 tests pass, ruff clean, ty type-check clean.

Security:
- Add tool_error_handler context manager (exceptions.py) — standardised
  error handling, eliminates 11 bare except-reraise patterns
- Remove unused exception subclasses (ConfigurationError, UnraidAPIError,
  SubscriptionError, ValidationError, IdempotentOperationError)
- Harden GraphQL subscription query validator with allow-list and
  forbidden-keyword regex (diagnostics.py)
- Add input validation for rclone create_remote config_data: injection,
  path-traversal, and key-count limits (rclone.py)
- Validate notifications importance enum before GraphQL request (notifications.py)
- Sanitise HTTP/network/JSON error messages — no raw exception strings
  leaked to clients (client.py)
- Strip path/creds from displayed API URL via _safe_display_url (health.py)
- Enable Ruff S (bandit) rule category in pyproject.toml
- Harden container mutations to strict-only matching — no fuzzy/substring
  for destructive operations (docker.py)

Performance:
- Token-bucket rate limiter (90 tokens, 9 req/s) with 429 retry backoff (client.py)
- Lazy asyncio.Lock init via _get_client_lock() — fixes event-loop
  module-load crash (client.py)
- Double-checked locking in get_http_client() for fast-path (client.py)
- Short hex container ID fast-path skips list fetch (docker.py)
- Cap resource_data log content to 1 MB / 5,000 lines (manager.py)
- Reset reconnect counter after 30 s stable connection (manager.py)
- Move tail_lines validation to module level; enforce 10,000 line cap
  (storage.py, docker.py)
- force_terminal=True removed from logging RichHandler (logging.py)

Architecture:
- Register diagnostic tools in server startup (server.py)
- Move ALL_ACTIONS computation to module level in all tools
- Consolidate format_kb / format_bytes into shared core/utils.py
- Add _safe_get() helper in core/utils.py for nested dict traversal
- Extract _analyze_subscription_status() from health.py diagnose handler
- Validate required config at startup — fail fast with CRITICAL log (server.py)

Code quality:
- Remove ~90 lines of dead Rich formatting helpers from logging.py
- Remove dead self.websocket attribute from SubscriptionManager
- Remove dead setup_uvicorn_logging() wrapper
- Move _VALID_IMPORTANCE to module level (N806 fix)
- Add slots=True to all three dataclasses (SubscriptionData, SystemHealth, APIResponse)
- Fix None rendering as literal "None" string in info.py summaries
- Change fuzzy-match log messages from INFO to DEBUG (docker.py)
- UTC-aware datetimes throughout (manager.py, diagnostics.py)

Infrastructure:
- Upgrade base image python:3.11-slim → python:3.12-slim (Dockerfile)
- Add non-root appuser (UID/GID 1000) with HEALTHCHECK (Dockerfile)
- Add read_only, cap_drop: ALL, tmpfs /tmp to docker-compose.yml
- Single-source version via importlib.metadata (pyproject.toml → __init__.py)
- Add open_timeout to all websockets.connect() calls

Tests:
- Update error message matchers to match sanitised messages (test_client.py)
- Fix patch targets for UNRAID_API_URL → utils module (test_subscriptions.py)
- Fix importance="info" → importance="normal" (test_notifications.py, http_layer)
- Fix naive datetime fixtures → UTC-aware (test_subscriptions.py)

Co-authored-by: Claude <claude@anthropic.com>

unraid_mcp/core/utils.py

@@ -0,0 +1,68 @@
+"""Shared utility functions for Unraid MCP tools."""
+
+from typing import Any
+
+
+def safe_get(data: dict[str, Any], *keys: str, default: Any = None) -> Any:
+    """Safely traverse nested dict keys, handling None intermediates.
+
+    Args:
+        data: The root dictionary to traverse.
+        *keys: Sequence of keys to follow.
+        default: Value to return if any key is missing or None.
+
+    Returns:
+        The value at the end of the key chain, or default if unreachable.
+    """
+    current = data
+    for key in keys:
+        if not isinstance(current, dict):
+            return default
+        current = current.get(key)
+    return current if current is not None else default
+
+
+def format_bytes(bytes_value: int | None) -> str:
+    """Format byte values into human-readable sizes.
+
+    Args:
+        bytes_value: Number of bytes, or None.
+
+    Returns:
+        Human-readable string like "1.00 GB" or "N/A" if input is None/invalid.
+    """
+    if bytes_value is None:
+        return "N/A"
+    try:
+        value = float(int(bytes_value))
+    except (ValueError, TypeError):
+        return "N/A"
+    for unit in ["B", "KB", "MB", "GB", "TB", "PB"]:
+        if value < 1024.0:
+            return f"{value:.2f} {unit}"
+        value /= 1024.0
+    return f"{value:.2f} EB"
+
+
+def format_kb(k: Any) -> str:
+    """Format kilobyte values into human-readable sizes.
+
+    Args:
+        k: Number of kilobytes, or None.
+
+    Returns:
+        Human-readable string like "1.00 GB" or "N/A" if input is None/invalid.
+    """
+    if k is None:
+        return "N/A"
+    try:
+        k = int(k)
+    except (ValueError, TypeError):
+        return "N/A"
+    if k >= 1024 * 1024 * 1024:
+        return f"{k / (1024 * 1024 * 1024):.2f} TB"
+    if k >= 1024 * 1024:
+        return f"{k / (1024 * 1024):.2f} GB"
+    if k >= 1024:
+        return f"{k / 1024:.2f} MB"
+    return f"{k} KB"