feat(01-01): sqlc config, tailwind input CSS, air live-reload config

- sqlc.yaml: postgresql engine, schema points at migrations/ (Pitfall 7), pgx/v5 sql_package
- tailwind.input.css: @source globs for templ + internal/web Go files (Pitfall 3), @imports four ui/*.css files per UI-SPEC
- .air.toml: watches .go + .templ, excludes generated *_templ.go (Pitfall 5), runs 'templ generate' pre-build
- Tailwind watch is NOT wired into air pre_cmd (two-terminal workflow per RESEARCH Open Q2)

backend/.air.toml

@@ -0,0 +1,11 @@
+root = "."
+tmp_dir = "tmp"
+
+[build]
+cmd = "templ generate && go build -o ./tmp/web ./cmd/web"
+bin = "./tmp/web"
+include_ext = ["go", "templ"]
+exclude_dir = ["tmp", "bin", "static", ".git", "internal/db/sqlc"]
+exclude_regex = [".*_templ\\.go$"]
+delay = 200
+stop_on_error = true

backend/sqlc.yaml

@@ -0,0 +1,12 @@
+version: "2"
+sql:
+  - engine: postgresql
+    schema: "migrations"
+    queries: "internal/db/queries"
+    gen:
+      go:
+        package: "sqlc"
+        out: "internal/db/sqlc"
+        sql_package: "pgx/v5"
+        emit_json_tags: false
+        emit_interface: false

backend/tailwind.input.css

@@ -0,0 +1,10 @@
+@import "tailwindcss";
+
+@source "../templates/**/*.templ";
+@source "../internal/web/**/*.templ";
+@source "../internal/web/**/*.go";
+
+@import "../internal/web/ui/base.css";
+@import "../internal/web/ui/button.css";
+@import "../internal/web/ui/card.css";
+@import "../internal/web/ui/badge.css";