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.

.gitignore

@@ -1,8 +1,34 @@
-c4
-c4.db
-data/
-.env
+# Allowlisting gitignore: ignore everything, then un-ignore what we track.
+# source: https://github.com/github/gitignore/blob/main/community/Golang/Go.AllowList.gitignore
 
-# Deploy artifacts
-c4-deploy-*.tar.gz
-c4-deploy-*_b64*.txt
+# Ignore everything
+*
+
+# But not these files...
+!.gitignore
+
+!*.go
+!*.sql
+!go.sum
+!go.mod
+!Taskfile.yml
+!sqlc.yaml
+!.golangci.yml
+!.gitea/workflows/*.yml
+
+!.env.example
+!LICENSE
+
+!assets/**/*
+
+# Generated CSS stays out of version control
+assets/css/output.css
+
+# Deploy scripts and configs
+!deploy/*.sh
+!deploy/*.service
+!docker-compose.yml
+!Dockerfile
+
+# ...even if they are in subdirectories
+!*/