Refactor to prometheus_client, JSON logging, and codebase cleanup

- Replace file-based metrics and HTTP server with prometheus_client
  (Gauge + start_http_server), eliminating file I/O race conditions
- Fix ThreadProbe and thread restart lambda bugs
- Switch logging from RotatingFileHandler to JSON stdout for fluentd/Loki
- Add PYTHONUNBUFFERED=1 to Dockerfile for immediate container log output
- Upgrade base image from python:3.12.3-slim to python:3.13-slim
- Upgrade pyvmomi to 9.0.0.0; pin pydantic>=2.9.0 and typing_extensions>=4.12.2
  to use pre-built Python 3.13 wheels (removes Rust toolchain from build)
- Remove unused packages: boto3, botocore, s3transfer, jmespath, redis,
  docopt, pyflakes, posthog
- Remove unused imports (Posthog, CaseInsensitiveDict) and dead variables
  (callhomestats, local_site_info, lastStats)
- Fix service_profile() NameError (siteidentifier -> serviceProfileIdentifier)
- Remove bare print() in zvma.py __authhandler__, replace with self.log.info()
- Remove all commented-out PostHog blocks from zvma10/zvma.py
- Delete legacy zvma9_7/ module and app/logs/ directory
- Remove deprecated 'version: 3.3' from docker-compose.yml

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/requirements.txt

@@ -1,28 +1,21 @@
+prometheus_client>=0.19.0
 annotated-types==0.6.0
 async-timeout==4.0.3
 backoff==2.2.1
-boto3==1.28.63
-botocore==1.31.63
 cachetools==5.3.1
 certifi==2023.7.22
 charset-normalizer==3.3.0
-docopt==0.6.2
 idna==3.4
-jmespath==1.0.1
 monotonic==1.6
-posthog==3.0.2
 prompt-toolkit==3.0.39
-pydantic
-pyflakes==3.1.0
+pydantic>=2.9.0
 Pygments==2.16.1
 python-dateutil==2.8.2
 pyvim==3.0.3
-pyvmomi==8.0.2.0
-redis==5.0.1
+pyvmomi==9.0.0.0
 requests==2.32.0
-s3transfer==0.7.0
 six==1.16.0
 tinydb==4.8.0
-typing_extensions==4.8.0
+typing_extensions>=4.12.2
 urllib3==2.0.6
 wcwidth==0.2.8