feat: add external API providers and central settings database

- Add central settings database client (system_settings on postgres-shared)
  - User-scoped settings with global fallback
  - API config storage with enabled/disabled toggle
  - Per-source category filtering for news

- Add modular external API providers in src/apis/:
  - OpenMeteoProvider: weather with geocoding (free, no key)
  - NOSProvider: Dutch news RSS feeds
  - BBCProvider: English news RSS feeds
  - AggregatedNewsProvider: merges sources with category filtering
  - AlphaVantageProvider: financial quotes (API key from settings DB)

- Add provider dependencies and lifecycle management
- Add requirements-dev.txt with pip-audit for security auditing
- Add MEMORY_REMEMBER_PLAN.md documenting volatile/document memory architecture

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

requirements-dev.txt

@@ -0,0 +1,12 @@
+# Development dependencies
+-r requirements.txt
+
+# Testing
+pytest~=8.3.0
+pytest-asyncio~=0.24.0
+
+# Security auditing
+pip-audit~=2.7.0
+
+# Code quality
+ruff~=0.8.0