feat: Add dynamic Git-based versioning system

- Add app/version.py module generating version from Git metadata
- Format: YYYY.MM.DD+<commit_hash> (e.g., 2025.01.18+576c8ca9)
- Add +dirty suffix for uncommitted changes (ignores .env, technotes/)
- Add /api/version endpoint for monitoring
- Display version in hamburger menu
- Add freeze mechanism for Docker builds

Deploy command updated:
git push && ssh ... "cd ~/mc-webui && git pull && python -m app.version freeze && docker compose up -d --build"

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/version.py

@@ -0,0 +1,70 @@
+"""
+Git-based version management for mc-webui.
+Format: YYYY.MM.DD+<short_hash> (e.g., 2025.01.18+576c8ca9)
+"""
+import subprocess
+import shlex
+import os
+
+VERSION_STRING = "0.0.0+unknown"
+DOCKER_TAG = "0.0.0-unknown"
+
+
+def subprocess_run(args):
+    """Execute subprocess and return stripped stdout."""
+    if not isinstance(args, (list, tuple)):
+        args = shlex.split(args)
+    proc = subprocess.run(
+        args,
+        capture_output=True,
+        text=True,
+        check=True,
+        env={"PATH": os.environ.get("PATH", ""), "LC_ALL": "C"}
+    )
+    return proc.stdout.strip()
+
+
+def get_git_version():
+    """Get version from git commit date and hash."""
+    # Get date (YYYY.MM.DD) and short hash
+    git_version = subprocess_run(
+        r"git show -s --date=format:%Y.%m.%d --format=%cd+%h"
+    )
+    # Keep full ISO format (with leading zeros)
+    docker_tag = git_version.replace("+", "-")
+
+    # Check for uncommitted changes (ignore .env and technotes/)
+    try:
+        subprocess_run("git diff --quiet -- . :!*.env :!.env :!technotes/")
+    except subprocess.CalledProcessError as e:
+        if e.returncode == 1:
+            git_version += "+dirty"
+
+    return git_version, docker_tag
+
+
+# Load version: frozen file takes priority, then git, then fallback
+try:
+    from app.version_frozen import VERSION_STRING, DOCKER_TAG
+except ImportError:
+    try:
+        VERSION_STRING, DOCKER_TAG = get_git_version()
+    except Exception:
+        pass  # Keep defaults
+
+
+if __name__ == "__main__":
+    import sys
+    if len(sys.argv) >= 2 and sys.argv[1] == "freeze":
+        VERSION_STRING, DOCKER_TAG = get_git_version()
+        code = f'''"""Frozen version - auto-generated, do not edit."""
+VERSION_STRING = "{VERSION_STRING}"
+DOCKER_TAG = "{DOCKER_TAG}"
+'''
+        path = os.path.join(os.path.dirname(__file__), "version_frozen.py")
+        with open(path, "w", encoding="utf8") as f:
+            f.write(code)
+        print(f"Version frozen: {VERSION_STRING}")
+    else:
+        print(f'VERSION_STRING="{VERSION_STRING}"')
+        print(f'DOCKER_TAG="{DOCKER_TAG}"')