Add org-agenda-api container builds and fly.io deployment

Consolidates container builds from colonelpanic-org-agenda-api repo:
- Add org-agenda-api input to nixos flake
- Add container-colonelpanic and container-kat package outputs
- Add org-agenda-api cachix as substituter
- Add org-agenda-api devShell for deployment work

New org-agenda-api directory contains:
- container.nix: Container build logic using mkContainer
- configs/: Instance configs (custom-config.el, fly.toml, secrets)
- deploy.sh: Fly.io deployment script
- secrets.nix: agenix secret declarations

Build with: nix build .#container-colonelpanic
Deploy with: cd org-agenda-api && ./deploy.sh colonelpanic

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

org-agenda-api/justfile

@@ -0,0 +1,35 @@
+# org-agenda-api commands
+
+base_url := "https://colonelpanic-org-agenda.fly.dev"
+user := "imalison"
+
+# Get all todos
+get-all-todos:
+    @curl -s -u "{{user}}:$(pass show org-agenda-api/imalison | head -1)" "{{base_url}}/get-all-todos" | jq .
+
+# Get today's agenda
+get-todays-agenda:
+    @curl -s -u "{{user}}:$(pass show org-agenda-api/imalison | head -1)" "{{base_url}}/get-todays-agenda" | jq .
+
+# Get agenda (day view)
+agenda:
+    @curl -s -u "{{user}}:$(pass show org-agenda-api/imalison | head -1)" "{{base_url}}/agenda" | jq .
+
+# Get agenda files
+agenda-files:
+    @curl -s -u "{{user}}:$(pass show org-agenda-api/imalison | head -1)" "{{base_url}}/agenda-files" | jq .
+
+# Get todo states
+todo-states:
+    @curl -s -u "{{user}}:$(pass show org-agenda-api/imalison | head -1)" "{{base_url}}/todo-states" | jq .
+
+# Health check
+health:
+    @curl -s "{{base_url}}/health" | jq .
+
+# Create a todo
+create-todo title:
+    @curl -s -X POST -u "{{user}}:$(pass show org-agenda-api/imalison | head -1)" \
+        -H "Content-Type: application/json" \
+        -d '{"title": "{{title}}"}' \
+        "{{base_url}}/create-todo" | jq .