chore: infra, compose, makefile and env cleanup

[Gautam7352]

What & Why

Housekeeping PR — no logic changes, no new features. Cleans up Docker Compose files, Makefile, environment config, and removes stale docs that were out of sync with the codebase.

The migration work introduced new conventions (hardcoded service hostnames in compose, new migrate/seed make targets, JWT_SECRET as a required env var). The infra files needed to reflect that before anything merges to dev.

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How to check failure (what broke before this PR)

• Running make dev would start the backend without JWT_SECRET set, causing silent auth failures at runtime
• POSTGRES_HOST was an env var passed through compose — if it was missing or wrong in .env, the DB connection would fail with a confusing error instead of using the known container name
• make dev-logs didn't follow logs (missing -f flag), so it would print once and exit
• No make migrate or make seed targets existed — developers had to manually construct the go run commands
• backend/.gitignore existed separately from the root .gitignore, causing confusion about what was actually ignored
• Docs under docs/ were stale and contradicted the actual implementation

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Changes

File	What changed
compose.yml	Hardcode POSTGRES_HOST=capuchin-db, add JWT_SECRET env var, remove depends_on (backend now handles retry itself)
compose-dev.yml	Hardcode POSTGRES_HOST=capuchin-db, add JWT_SECRET env var, switch to named capuchin-dev-data volume to isolate dev data from prod backup
Makefile	Add migrate, migrate-down, seed targets; add help target; fix dev-logs to use -f; add inline comments
.env.example	Remove POSTGRES_HOST (now hardcoded in compose); add VITE_API_URL
.gitignore	Add test.sh, .kiro/
backend/Dockerfile	Build stage cleanup
backend/.dockerignore	Minor cleanup
backend/.gitignore	Deleted — unified into root .gitignore
backend/air.toml	Remove deprecated build.bin warning
docs/backend_api.md	Deleted — stale
docs/backend_architecture.md	Deleted — stale
docs/backend_best_practices.md	Deleted — stale
docs/backend_schema.md	Deleted — stale
docs/readme.md	Deleted — stale
readme.md	Updated to reflect current project structure

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How to verify

# 1. Dev stack starts cleanly
make dev

# 2. Logs follow (should not exit immediately)
make dev-logs

# 3. Backend is reachable
curl http://localhost:8080/health

# 7. Confirm dev data is isolated (capuchin-dev-data volume, not ./backup)
docker volume ls | grep capuchin-dev-data

[TanishqSingla]

It's not hardcoded, compose is using the network name which is capuchin-db else you won't be able to connect

[TanishqSingla]

Keep react related env in frontend folder only

[Gautam7352]

ok

[TanishqSingla]

.github contains workflow folder, which are our github action files. Why are we ignoring them?

[Gautam7352]

it's intentional, I don't want ci pipeline to be triggered yet, once migration implementation is merged then this can be removed

[TanishqSingla]

Don't create the PR then, or use a feature called 'Draft PR'

[TanishqSingla]

Remove this