chore: gitignore local/AI tooling files and untrack prompts.db

Add .claude/, .serena/, .playwright-mcp/, logs/, docs/, AGENTS.md,
CLAUDE.md, standalone_tagger.py, and prompts.db to .gitignore.
Untrack prompts.db so local database changes don't pollute diffs.

.gitignore

@@ -1,6 +1,19 @@
 # Tailwind standalone CLI (downloaded by `make css-setup`)
 tailwindcss
 
+# AI tooling / local config
+.claude/
+.playwright-mcp/
+.serena/
+AGENTS.md
+CLAUDE.md
+
+# Local files
+docs/
+logs/
+standalone_tagger.py
+prompts.db
+
 # Byte-compiled / optimized / DLL files
 __pycache__/
 *.py[cod]