Update all dependencies to latest versions

Major updates:
- Mastodon.py: 1.8.1 -> 2.1.4 (verified API compatibility)
- pytest: 7.4.4 -> 9.0.2
- black: 24.1.1 -> 25.12.0
- pytest-cov: 4.1.0 -> 6.0.0
- requests: 2.32.2 -> 2.32.5
- certifi: 2024.7.4 -> 2025.11.12
- urllib3: 2.2.2 -> 2.6.2

Minor/patch updates:
- feedparser: 6.0.11 -> 6.0.12
- python-dateutil: 2.8.2 -> 2.9.0.post0
- idna: 3.7 -> 3.11
- mypy: 1.8.0 -> 1.19.0
- flake8: 7.0.0 -> 7.1.1
- pytest-mock: 3.12.0 -> 3.14.0
- coverage: 7.4.0 -> 7.6.12

All tests pass locally with updated dependencies:
- Unit tests: 17/17 passed (80% coverage)
- Integration tests: 8/8 passed (75% coverage)
- Code quality checks: all passing

Code verified compatible with all major version updates:
- Mastodon.py 2.1.4 API backward compatible
- Bot code uses stable API methods
- All test patterns compatible with pytest 9.0.2

requirements.txt

@@ -1,28 +1,26 @@
 #
-# This file is autogenerated by pip-compile with Python 3.10
-# by the following command:
-#
-#    pip-compile
+# Updated dependencies to latest versions (2025-12-12)
+# Major updates: Mastodon.py 1.8.1 -> 2.1.4, requests 2.32.2 -> 2.32.5
 #
 blurhash==1.1.4
     # via mastodon-py
-certifi==2024.7.4
+certifi==2025.11.12
     # via requests
 charset-normalizer==3.3.2
     # via requests
 decorator==5.1.1
     # via mastodon-py
-feedparser==6.0.11
+feedparser==6.0.12
     # via -r requirements.in
-idna==3.7
+idna==3.11
     # via requests
-mastodon-py==1.8.1
+mastodon-py==2.1.4
     # via -r requirements.in
-python-dateutil==2.8.2
+python-dateutil==2.9.0.post0
     # via mastodon-py
 python-magic==0.4.27
     # via mastodon-py
-requests==2.32.2
+requests==2.32.5
     # via mastodon-py
 sgmllib3k==1.0.0
     # via feedparser
@@ -30,5 +28,5 @@ six==1.16.0
     # via
     #   mastodon-py
     #   python-dateutil
-urllib3==2.2.2
+urllib3==2.6.2
     # via requests