ci: add GitHub Actions lint and test pipeline [FASE-0.6]

Run ruff and pytest against Postgres and Redis service containers; document CI in README.

.github/workflows/ci.yml

@@ -54,7 +54,7 @@ jobs:
           pip install ruff
 
       - name: Lint
-        run: ruff check app/
+        run: ruff check app/ tests/
 
       - name: Test
         env:

README.md

@@ -1,5 +1,7 @@
 # Aegis — MITRE ATT&CK Coverage Platform
 
+Continuous integration (lint + tests against PostgreSQL and Redis) is defined in [`.github/workflows/ci.yml`](.github/workflows/ci.yml).
+
 Aegis is a comprehensive platform for tracking and managing security coverage against the MITRE ATT&CK framework. It enables security teams to document, validate, and visualize their defensive capabilities against known adversary techniques through a structured Red Team / Blue Team validation workflow.
 
 ## Features