trusted proxy, TOTP replay protection, new tests

- Trusted proxy config option for proxy-aware IP extraction
  used by rate limiting and audit logs; validates proxy IP
  before trusting X-Forwarded-For / X-Real-IP headers
- TOTP replay protection via counter-based validation to
  reject reused codes within the same time step (±30s)
- RateLimit middleware updated to extract client IP from
  proxy headers without IP spoofing risk
- New tests for ClientIP proxy logic (spoofed headers,
  fallback) and extended rate-limit proxy coverage
- HTMX error banner script integrated into web UI base
- .gitignore updated for mciasdb build artifact

Security: resolves CRIT-01 (TOTP replay attack) and
DEF-03 (proxy-unaware rate limiting); gRPC TOTP
enrollment aligned with REST via StorePendingTOTP

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

CLAUDE.md

@@ -74,6 +74,26 @@ This is a security-critical project. The following rules are non-negotiable:
 - Prefer explicit error handling over panics; never silently discard errors
 - Use `log/slog` (or goutils equivalents) for structured logging; never `fmt.Println` in production paths
 
+## Verification
+
+After any code edit, always verify the fix by running `go build ./...` and `go test ./...` before claiming the issue is resolved. Never claim lint/tests pass without actually running them.
+
+## Database
+
+When working with migrations (golang-migrate or SQLite), always test migrations against a fresh database AND an existing database to catch duplicate column/table errors. SQLite does not support IF NOT EXISTS for ALTER TABLE.
+
+## File Editing
+
+Before editing files, re-read the current on-disk version to confirm it matches expectations. If files seem inconsistent, stop and flag this to the user before proceeding.
+
+## Project Context
+
+For this project (MCIAS): Go codebase, uses golang-migrate, SQLite (with shared-cache for in-memory), htmx frontend with Go html/template, golangci-lint (use `go vet` if version incompatible), and cert tool for TLS certificates. Check `docs/` for tool-specific usage before guessing CLI flags.
+
+## UI Development
+
+When implementing UI features, ensure they work for the empty-state case (e.g., no credentials exist yet, no accounts created). Always test with zero records.
+
 ## Key Documents
 
 - `PROJECT.md` — Project specifications and requirements