v0.3.0: rename app Daybook -> AgentFeed

Removes the "Daybook" name from everything user- and agent-facing, since no
agents are configured yet and this is the cheap moment to do it.

- UI brand, docs, README, CLAUDE.md -> AgentFeed.
- Ingest env vars DAYBOOK_URL/TOKEN/SOURCE/DATA_DIR/BIND_ADDR/HOST_DATA_DIR/
  KEY_PROVISIONING_API -> AGENTFEED_* (token *values* unchanged).
- Skill: skills/daybook-posting -> skills/agentfeed-posting, daybook_post.py
  -> agentfeed_post.py (+ scripts/ wrapper and its test).
- static/daybook.css -> static/agentfeed.css; localStorage daybook.* ->
  agentfeed.*; templatetag daybook_extras -> agentfeed_extras; multipart
  boundaries; json/csv viewer element ids; daybook_exception_handler ->
  agentfeed_exception_handler; compose service/container -> agentfeed.
- Key-provisioning API now OFF by default (independent of DEBUG); enable with
  AGENTFEED_KEY_PROVISIONING_API=1 on test installs only.
- Posting helper now points at Settings -> API Keys.

Deferred on purpose (a later, separate step): the Django package
`daybook_project`, the `/opt/daybook` install path, and the Forgejo repo name.
The sibling AGENT_DAYBOOK__LLM_TEST name is intentionally untouched.

Full suite: 129 passing; live server verified serving under the new name.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

scripts/seed_demo_artifacts.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 """Post one demo artifact of every kind, tagged, dated today.
 
-Posts through the real ingest API using the existing daybook_post.py helper,
+Posts through the real ingest API using the existing agentfeed_post.py helper,
 so seeded data goes through the same normalization as real agent output.
 
 Usage (from project root, with the dev server running):
@@ -13,7 +13,7 @@ import sys
 import tempfile
 from pathlib import Path
 
-HELPER = Path(__file__).resolve().parent.parent / "skills" / "daybook-posting" / "scripts" / "daybook_post.py"
+HELPER = Path(__file__).resolve().parent.parent / "skills" / "agentfeed-posting" / "scripts" / "agentfeed_post.py"
 PERSONA = "seed-demo"
 TAGS = "seed-demo,demo"