fix: Resolve v1.1.2-rc.1 production issues - Static files and metrics

This release candidate fixes two critical production issues discovered in v1.1.2-rc.1:

1. CRITICAL: Static files returning 500 errors
   - HTTP monitoring middleware was accessing response.data on streaming responses
   - Fixed by checking direct_passthrough flag before accessing response data
   - Static files (CSS, JS, images) now load correctly
   - File: starpunk/monitoring/http.py

2. HIGH: Database metrics showing zero
   - Configuration key mismatch: config set METRICS_SAMPLING_RATE (singular),
     buffer read METRICS_SAMPLING_RATES (plural)
   - Fixed by standardizing on singular key name
   - Modified MetricsBuffer to accept both float and dict for flexibility
   - Changed default sampling from 10% to 100% for better visibility
   - Files: starpunk/monitoring/metrics.py, starpunk/config.py

Version: 1.1.2-rc.2

Documentation:
- Investigation report: docs/reports/2025-11-28-v1.1.2-rc.1-production-issues.md
- Architect review: docs/reviews/2025-11-28-v1.1.2-rc.1-architect-review.md
- Implementation report: docs/reports/2025-11-28-v1.1.2-rc.2-fixes.md

Testing: All monitoring tests pass (28/28)

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

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

CHANGELOG.md

@@ -7,6 +7,30 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [1.1.2-rc.2] - 2025-11-28
+
+### Fixed
+- **CRITICAL**: Static files now load correctly - fixed HTTP middleware streaming response handling
+  - HTTP metrics middleware was accessing `.data` on streaming responses (Flask's `send_from_directory`)
+  - This caused RuntimeError: "Attempted implicit sequence conversion but the response object is in direct passthrough mode"
+  - Now checks `direct_passthrough` attribute before accessing response data
+  - Gracefully falls back to `content_length` for streaming responses
+  - Fixes complete site failure (no CSS/JS loading)
+
+- **HIGH**: Database metrics now display correctly - fixed configuration key mismatch
+  - Config sets `METRICS_SAMPLING_RATE` (singular), metrics read `METRICS_SAMPLING_RATES` (plural)
+  - Mismatch caused fallback to hardcoded 10% sampling regardless of config
+  - Fixed key to use `METRICS_SAMPLING_RATE` (singular) consistently
+  - MetricsBuffer now accepts both float (global rate) and dict (per-type rates)
+  - Increased default sampling rate from 10% to 100% for low-traffic sites
+
+### Changed
+- Default metrics sampling rate increased from 10% to 100%
+  - Better visibility for low-traffic single-user deployments
+  - Configurable via `METRICS_SAMPLING_RATE` environment variable (0.0-1.0)
+  - Minimal overhead at typical usage levels
+  - Power users can reduce if needed
+
 ## [1.1.2-dev] - 2025-11-27
 
 ### Added - Phase 3: Feed Statistics Dashboard & OPML Export (Complete)