fix: rebase onto main, fix SQLite concurrency, lint clean

- Add busy_timeout PRAGMA and MaxOpenConns(1) for SQLite stability
- Use per-test temp DB in handler tests to prevent state leaks
- Pre-allocate migrations slice (prealloc lint)
- Remove invalid linter names (wsl_v5, noinlineerr) from .golangci.yml
- Remove unused //nolint:gosec directives
- Replace context.Background() with t.Context() in tests
- Use goimports formatting for all files
- All make check passes with zero failures

cmd/chat-cli/main.go

@@ -12,10 +12,10 @@ import (
 )
 
 const (
-	splitParts   = 2
-	pollTimeout  = 15
-	pollRetry    = 2 * time.Second
-	timeFormat   = "15:04"
+	splitParts  = 2
+	pollTimeout = 15
+	pollRetry   = 2 * time.Second
+	timeFormat  = "15:04"
 )
 
 // App holds the application state.