feat: MLOps external services, AI stack planning, admin MLOps hub

Infrastructure:
- Add `mlops` compose profile: MLflow (basic-auth, /mlflow path) + Airflow (LocalExecutor, /airflow path) + airflow-db
- infra/mlflow/basic_auth.ini for MLflow auth config
- Caddy routes /mlflow* and /airflow* inside existing o.alogins.net block (see agap_git)
- Dockerfile.admin: NEXT_PUBLIC_MLFLOW_URL / NEXT_PUBLIC_AIRFLOW_URL build args (default /mlflow, /airflow)

Admin panel:
- /admin/models: replace MLflow iframe with external link cards
- /admin/experiments: replace LinUCB stats with MLOps hub (links to MLflow experiments/models + Airflow DAGs/datasets)
- AdminShell: external nav links for MLflow ↗ and Airflow ↗ under MLOps section

Docs & planning:
- README: new AI stack section (Ollama/LiteLLM/OpenWebUI three-tier, tip generation pipeline, model aliases)
- README: Phase 2 expanded with AI infra issues (#86-#93) and granular pipeline breakdown
- README: Phase 4 expanded with LLM MLOps items (#94-#97)
- CLAUDE.md: AI stack section, updated current phase (M1 shipped / M2 in progress), compose profiles, updated What NOT to do
- docs/architecture/overview.md: AI stack section, updated decision flow diagram for Phase 2 LLM pipeline
- ADR-0006: updated to reflect external services (path-based, not embedded)
- Gitea issues #86-#97 created (M2: AI infra + pipeline; M4: LLM MLOps)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pnpm-lock.yaml

@@ -45,9 +45,6 @@ importers:
         specifier: ^2.15.3
         version: 2.15.4(react-dom@19.2.5(react@19.2.5))(react@19.2.5)
     devDependencies:
-      '@types/marked':
-        specifier: ^6.0.0
-        version: 6.0.0
       '@types/node':
         specifier: ^22.10.5
         version: 22.19.17
@@ -1335,10 +1332,6 @@ packages:
   '@types/http-errors@2.0.5':
     resolution: {integrity: sha512-r8Tayk8HJnX0FztbZN7oVqGccWgw98T/0neJphO91KkmOzug1KkofZURD4UaD5uH8AqcFLfdPErnBod0u71/qg==}
 
-  '@types/marked@6.0.0':
-    resolution: {integrity: sha512-jmjpa4BwUsmhxcfsgUit/7A9KbrC48Q0q8KvnY107ogcjGgTFDlIL3RpihNpx2Mu1hM4mdFQjoVc4O6JoGKHsA==}
-    deprecated: This is a stub types definition. marked provides its own type definitions, so you do not need this installed.
-
   '@types/node@22.19.17':
     resolution: {integrity: sha512-wGdMcf+vPYM6jikpS/qhg6WiqSV/OhG+jeeHT/KlVqxYfD40iYJf9/AE1uQxVWFvU7MipKRkRv8NSHiCGgPr8Q==}
 
@@ -3817,10 +3810,6 @@ snapshots:
 
   '@types/http-errors@2.0.5': {}
 
-  '@types/marked@6.0.0':
-    dependencies:
-      marked: 14.1.4
-
   '@types/node@22.19.17':
     dependencies:
       undici-types: 6.21.0