feat: add component-aware RFC 5424 application logging system

- Modify Rfc5424Formatter to read decnet_component from LogRecord
  and use it as RFC 5424 APP-NAME field (falls back to 'decnet')
- Add get_logger(component) factory in decnet/logging/__init__.py
  with _ComponentFilter that injects decnet_component on each record
- Wire all five layers to their component tag:
    cli -> 'cli', engine -> 'engine', api -> 'api' (api.py, ingester,
    routers), mutator -> 'mutator', collector -> 'collector'
- Add structured INFO/DEBUG/WARNING/ERROR log calls throughout each
  layer per the defined vocabulary; DEBUG calls are suppressed unless
  DECNET_DEVELOPER=true
- Add tests/test_logging.py covering factory, filter, formatter
  component-awareness, fallback behaviour, and level gating

decnet/mutator/engine.py

@@ -14,12 +14,14 @@ from decnet.fleet import all_service_names
 from decnet.composer import write_compose
 from decnet.config import DeckyConfig, DecnetConfig
 from decnet.engine import _compose_with_retry
+from decnet.logging import get_logger
 
 from pathlib import Path
 import anyio
 import asyncio
 from decnet.web.db.repository import BaseRepository
 
+log = get_logger("mutator")
 console = Console()
 
 
@@ -28,8 +30,10 @@ async def mutate_decky(decky_name: str, repo: BaseRepository) -> bool:
     Perform an Intra-Archetype Shuffle for a specific decky.
     Returns True if mutation succeeded, False otherwise.
     """
+    log.debug("mutate_decky: start decky=%s", decky_name)
     state_dict = await repo.get_state("deployment")
     if state_dict is None:
+        log.error("mutate_decky: no active deployment found in database")
         console.print("[red]No active deployment found in database.[/]")
         return False
 
@@ -73,12 +77,14 @@ async def mutate_decky(decky_name: str, repo: BaseRepository) -> bool:
     # Still writes files for Docker to use
     write_compose(config, compose_path)
 
+    log.info("mutation applied decky=%s services=%s", decky_name, ",".join(decky.services))
     console.print(f"[cyan]Mutating '{decky_name}' to services: {', '.join(decky.services)}[/]")
 
     try:
         # Wrap blocking call in thread
         await anyio.to_thread.run_sync(_compose_with_retry, "up", "-d", "--remove-orphans", compose_path)
     except Exception as e:
+        log.error("mutation failed decky=%s error=%s", decky_name, e)
         console.print(f"[red]Failed to mutate '{decky_name}': {e}[/]")
         return False
 
@@ -90,8 +96,10 @@ async def mutate_all(repo: BaseRepository, force: bool = False) -> None:
     Check all deckies and mutate those that are due.
     If force=True, mutates all deckies regardless of schedule.
     """
+    log.debug("mutate_all: start force=%s", force)
     state_dict = await repo.get_state("deployment")
     if state_dict is None:
+        log.error("mutate_all: no active deployment found")
         console.print("[red]No active deployment found.[/]")
         return
 
@@ -116,15 +124,20 @@ async def mutate_all(repo: BaseRepository, force: bool = False) -> None:
                 mutated_count += 1
 
     if mutated_count == 0 and not force:
+        log.debug("mutate_all: no deckies due for mutation")
         console.print("[dim]No deckies are due for mutation.[/]")
+    else:
+        log.info("mutate_all: complete mutated_count=%d", mutated_count)
 
 
 async def run_watch_loop(repo: BaseRepository, poll_interval_secs: int = 10) -> None:
     """Run an infinite loop checking for deckies that need mutation."""
+    log.info("mutator watch loop started poll_interval_secs=%d", poll_interval_secs)
     console.print(f"[green]DECNET Mutator Watcher started (polling every {poll_interval_secs}s).[/]")
     try:
         while True:
             await mutate_all(force=False, repo=repo)
             await asyncio.sleep(poll_interval_secs)
     except KeyboardInterrupt:
+        log.info("mutator watch loop stopped")
         console.print("\n[dim]Mutator watcher stopped.[/]")