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

Makefile

@@ -1,20 +1,49 @@
-VERSION := $(shell git describe --tags --always --dirty 2>/dev/null || echo "dev")
-LDFLAGS := -ldflags "-X main.Version=$(VERSION)"
+.PHONY: all build lint fmt fmt-check test check clean run debug docker hooks
 
-.PHONY: build test clean docker lint
+BINARY := chatd
+VERSION := $(shell git describe --tags --always --dirty 2>/dev/null || echo "dev")
+BUILDARCH := $(shell go env GOARCH)
+LDFLAGS := -X main.Version=$(VERSION) -X main.Buildarch=$(BUILDARCH)
+
+all: check build
 
 build:
-	go build $(LDFLAGS) -o chatd ./cmd/chatd/
-	go build $(LDFLAGS) -o chat-cli ./cmd/chat-cli/
-
-test:
-	DBURL="file::memory:?cache=shared" go test ./...
-
-clean:
-	rm -f chatd chat-cli
+	go build -ldflags "$(LDFLAGS)" -o bin/$(BINARY) ./cmd/chatd
 
 lint:
-	GOFLAGS=-buildvcs=false golangci-lint run ./...
+	golangci-lint run --config .golangci.yml ./...
+
+fmt:
+	gofmt -s -w .
+	goimports -w .
+
+fmt-check:
+	@test -z "$$(gofmt -l .)" || (echo "Files not formatted:" && gofmt -l . && exit 1)
+
+test:
+	go test -timeout 30s -v -race -cover ./...
+
+# check runs all validation without making changes
+# Used by CI and Docker build — fails if anything is wrong
+check: test lint fmt-check
+	@echo "==> Building..."
+	go build -ldflags "$(LDFLAGS)" -o /dev/null ./cmd/chatd
+	@echo "==> All checks passed!"
+
+run: build
+	./bin/$(BINARY)
+
+debug: build
+	DEBUG=1 GOTRACEBACK=all ./bin/$(BINARY)
+
+clean:
+	rm -rf bin/ chatd data.db
 
 docker:
-	docker build -t chat:$(VERSION) .
+	docker build -t chat .
+
+hooks:
+	@printf '#!/bin/sh\nset -e\n' > .git/hooks/pre-commit
+	@printf 'go mod tidy\ngo fmt ./...\ngit diff --exit-code -- go.mod go.sum || { echo "go mod tidy changed files; please stage and retry"; exit 1; }\n' >> .git/hooks/pre-commit
+	@printf 'make check\n' >> .git/hooks/pre-commit
+	@chmod +x .git/hooks/pre-commit