chore: add docker infrastructure, gists feature, attachment system, and admin CLI tools

- Add .dockerignore, Dockerfile, and docker compose targets to Makefile for containerized deployment
- Implement gists router with CRUD operations, database schema, and polymorphic comment/vote reuse
- Create attachment upload system with thumbnail generation, MIME detection, and storage path management
- Add attachments_prune CLI command to clean orphaned attachment records and files
- Introduce rate limiting middleware with 60 requests per minute window
- Add custom 404 and 500 error handlers with SEO-optimized template responses
- Extend database initialization with gists and attachments indexes plus upload site settings defaults
- Update load_comments to include attachment mapping for comment resources
- Register gists and uploads routers in main application and update AGENTS.md documentation

tests/test_attachments.py

@@ -0,0 +1,40 @@
+import pytest
+from pathlib import Path
+
+
+def test_attachment_upload_endpoint(alice):
+    page, user = alice
+    page.goto(f"{pytest.BASE_URL}/feed", wait_until="domcontentloaded")
+    page.locator(".feed-fab").first.wait_for(state="visible", timeout=10000)
+    page.locator(".feed-fab").click()
+    page.locator("#create-post-modal").wait_for(state="visible")
+
+
+def test_attachment_store_and_serve(alice):
+    page, user = alice
+    uploads = page.context.request.post(f"{pytest.BASE_URL}/attachments/upload")
+
+
+def test_post_attachments_display(alice):
+    page, user = alice
+    page.goto(f"{pytest.BASE_URL}/feed", wait_until="domcontentloaded")
+
+
+def test_project_attachments_display(alice):
+    page, user = alice
+    page.goto(f"{pytest.BASE_URL}/projects", wait_until="domcontentloaded")
+
+
+def test_bug_attachments_display(alice):
+    page, user = alice
+    page.goto(f"{pytest.BASE_URL}/bugs", wait_until="domcontentloaded")
+
+
+def test_attachment_uploader_component_present(alice):
+    page, user = alice
+    page.goto(f"{pytest.BASE_URL}/feed", wait_until="domcontentloaded")
+    page.locator(".feed-fab").wait_for(state="visible", timeout=10000)
+    page.locator(".feed-fab").click()
+    page.locator("#create-post-modal").wait_for(state="visible")
+    page.locator(".attachment-upload-area").wait_for(state="visible", timeout=5000)
+    page.locator(".attachment-upload-btn").wait_for(state="visible", timeout=5000)