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.

Makefile

@@ -1,24 +1,33 @@
-.PHONY: build run test clean docker docker-run lint vet
-
 BINARY=worktime-bot
 BUILD_DIR=.build
 
-build: $(BUILD_DIR)/$(BINARY)
+.PHONY: all build run test clean fmt tidy vet check docker docker-run
 
-$(BUILD_DIR)/$(BINARY): cmd/bot/*.go internal/**/*.go go.mod go.sum
-	mkdir -p $(BUILD_DIR)
+all: build test check
+
+build:
 	go build -o $(BUILD_DIR)/$(BINARY) ./cmd/bot/
 
 run: build
 	$(BUILD_DIR)/$(BINARY)
 
+run-dev:
+	go run ./cmd/bot/
+
 test:
 	go test ./...
 
-lint: vet
+fmt:
+	go fmt ./...
+
+tidy:
+	go mod tidy
+
 vet:
 	go vet ./...
 
+check: fmt vet
+
 clean:
 	rm -rf $(BUILD_DIR)
 
@@ -27,6 +36,3 @@ docker:
 
 docker-run: docker
 	docker compose up -d
-
-.PHONY: all
-all: build test lint