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.

db/sqlc.yaml

@@ -5,5 +5,9 @@ sql:
     schema: "migrations"
     gen:
       go:
-        package: "gen"
-        out: "gen"
+        package: "repository"
+        out: "repository"
+        emit_db_tags: true
+        emit_json_tags: true
+        emit_result_struct_pointers: true
+        emit_pointers_for_null_types: true