Rename app from chat to neoirc, binary to neoircd (closes #46)

- Rename Go module path: git.eeqj.de/sneak/chat -> git.eeqj.de/sneak/neoirc
- Rename binary: chatd -> neoircd, chat-cli -> neoirc-cli
- Rename cmd directories: cmd/chatd -> cmd/neoircd, cmd/chat-cli -> cmd/neoirc-cli
- Rename Go package: chatapi -> neoircapi
- Update Makefile: binary name, build targets, docker image tag, clean target
- Update Dockerfile: binary paths, user/group names, ENTRYPOINT
- Update .gitignore and .dockerignore
- Update all Go imports and doc comments
- Update default server name fallback: chat -> neoirc
- Update web client: localStorage keys, page title, default server name
- Update all schema $id URLs and example hostnames
- Update README.md: project name, binary references, examples, directory tree
- Update AGENTS.md: build command reference
- Update test fixtures: app name and channel names

.gitignore

@@ -21,7 +21,7 @@ node_modules/
 *.key
 
 # Build artifacts
-/chatd
+/neoircd
 /bin/
 *.exe
 *.dll
@@ -34,5 +34,5 @@ vendor/
 # Project
 data.db
 debug.log
-/chat-cli
+/neoirc-cli
 web/node_modules/