refactor: export full Gregorian range, add timezone fallback, cleanup rate limit, configurable schema path

- GenerateMonthlyReport now takes explicit Gregorian start/end range,
  computed via monthGregorianRange, so Jalali/Hijri months spanning
  two Gregorian months are fully covered in exports.
- Added loadLocation helper (UTC fallback on error) and replaced all
  11 ignored-error call sites in handlers + export.
- Added periodicCleanup goroutine in NewHandler to prevent unbounded
  growth of the rateLimit map.
- schemaPath is now read from SCHEMA_PATH env var (init), defaulting
  to /app/db/schema.sql.
- Migrated sendDayView to use sendOrEdit helper, removing duplicated
  send/edit branching.
- Removed dead code: userYearMonthToGregorian (unused), the old
  startOffset function (replaced).
- Updated README with calendar docs, new env vars, full project tree.
- Updated .env.example and docker-compose.yml with SCHEMA_PATH.
- Simplified Makefile: added fmt, tidy, check, run-dev targets;
  removed broken Make-glob prerequisite pattern.

internal/db/store.go

@@ -11,7 +11,14 @@ import (
 
 const driverName = "sqlite"
 
-var schemaPath = "/app/db/schema.sql"
+var schemaPath string
+
+func init() {
+	schemaPath = os.Getenv("SCHEMA_PATH")
+	if schemaPath == "" {
+		schemaPath = "/app/db/schema.sql"
+	}
+}
 
 type Store struct {
 	db *sql.DB