feat: Add AI-driven auto-update & restructure into package

The monolithic check_updates.py has been split into the update_monitor/
package with separate modules for fetching, extraction, comparison,
classification, and notification. This makes the codebase easier to
navigate and test.

The flat services.yaml is replaced by per-service directories under
services/<name>/config.yaml, co-locating config with update scripts
and AI review examples.

When --auto-update is enabled, services with an auto-update.sh script
get their release notes classified by a local Ollama model (using
few-shot examples from review-examples/) to decide whether the update
can be applied automatically or needs manual admin intervention. Results
are reported in a single consolidated Matrix message.

Immich is the first service with auto-update configured, using 7
real release note examples to train the classifier.

update_monitor/models.py

@@ -0,0 +1,25 @@
+from dataclasses import dataclass, field
+from pathlib import Path
+from typing import Any, Dict, Optional
+
+
+@dataclass
+class ExtractRule:
+    type: str
+    value: str
+
+
+@dataclass
+class ServiceConfig:
+    name: str
+    base_url: str
+    current_version_url: Optional[str]
+    current_version_extract: Optional[ExtractRule]
+    current_version_headers: Optional[Dict[str, str]]
+    upstream_latest_version_url: Optional[str]
+    upstream_latest_extract: Optional[ExtractRule]
+    upstream_latest_headers: Optional[Dict[str, str]]
+    notes: Optional[str]
+    login: Optional[Dict[str, Any]]
+    login_socket: Optional[Dict[str, Any]]
+    service_dir: Optional[Path] = field(default=None)