refactor: adopt portigo infrastructure patterns

Add config package with build-tag-switched dev/prod environments,
structured logging via zerolog, Taskfile for dev workflow, golangci-lint
config, testutil package, and improved DB setup with proper SQLite
pragmas and cleanup. Rename sqlc output package from gen to repository.

Switch to allowlist .gitignore, Alpine+UPX+scratch Dockerfile, and
CI pipeline with test/lint gates before deploy.

Taskfile.yml

@@ -0,0 +1,63 @@
+version: "3"
+
+tasks:
+  build:styles:
+    desc: Build TailwindCSS styles
+    cmds:
+      - go tool gotailwind -i assets/css/input.css -o assets/css/output.css --minify
+    sources:
+      - "assets/css/input.css"
+      - "**/*.go"
+    generates:
+      - "assets/css/output.css"
+
+  build:
+    desc: Production build to bin/c4
+    cmds:
+      - go build -o bin/c4 .
+    deps:
+      - build:styles
+
+  live:styles:
+    desc: Watch and rebuild TailwindCSS styles
+    cmds:
+      - go tool gotailwind -i assets/css/input.css -o assets/css/output.css -w
+
+  live:server:
+    desc: Run server with hot-reload via air
+    cmds:
+      - |
+        go tool air  \
+         -build.cmd "go build -tags=dev -o tmp/bin/c4 ." \
+         -build.bin "tmp/bin/c4" \
+         -build.exclude_dir "data,bin,tmp,deploy" \
+         -build.include_ext "go" \
+         -misc.clean_on_exit "true"
+
+  live:
+    desc: Dev mode with hot-reload
+    deps:
+      - live:styles
+      - live:server
+
+  test:
+    desc: Run the test suite
+    cmds:
+      - go test ./...
+
+  lint:
+    desc: Run golangci-lint
+    cmds:
+      - golangci-lint run
+
+  run:
+    desc: Build and run the server
+    cmds:
+      - ./bin/c4
+    deps:
+      - build
+
+  default:
+    desc: Run the default task (live)
+    cmds:
+      - task: live