fix: clear all addressable technical debt (DEBT-005 through DEBT-025)

Security:
- DEBT-008: remove query-string token auth; header-only Bearer now enforced
- DEBT-013: add regex constraint ^[a-z0-9\-]{1,64}$ on decky_name path param
- DEBT-015: stop leaking raw exception detail to API clients; log server-side
- DEBT-016: validate search (max_length=512) and datetime params with regex

Reliability:
- DEBT-014: wrap SSE event_generator in try/except; yield error frame on failure
- DEBT-017: emit log.warning/error on DB init retry; silent failures now visible

Observability / Docs:
- DEBT-020: add 401/422 response declarations to all route decorators

Infrastructure:
- DEBT-018: add HEALTHCHECK to all 24 template Dockerfiles
- DEBT-019: add USER decnet + setcap cap_net_bind_service to all 24 Dockerfiles
- DEBT-024: bump Redis template version 7.0.12 → 7.2.7

Config:
- DEBT-012: validate DECNET_API_PORT and DECNET_WEB_PORT range (1-65535)

Code quality:
- DEBT-010: delete 22 duplicate decnet_logging.py copies; deployer injects canonical
- DEBT-022: closed as false positive (print only in module docstring)
- DEBT-009: closed as false positive (templates already use structured syslog_line)

Build:
- DEBT-025: generate requirements.lock via pip freeze

Testing:
- DEBT-005/006/007: comprehensive test suite added across tests/api/
- conftest: in-memory SQLite + StaticPool + monkeypatched session_factory
- fuzz mark added; default run excludes fuzz; -n logical parallelism

DEBT.md updated: 23/25 items closed; DEBT-011 (Alembic) and DEBT-023 (digest pinning) remain

decnet/web/router/fleet/api_mutate_decky.py

@@ -1,4 +1,4 @@
-from fastapi import APIRouter, Depends, HTTPException
+from fastapi import APIRouter, Depends, HTTPException, Path
 
 from decnet.mutator import mutate_decky
 from decnet.web.dependencies import get_current_user
@@ -7,7 +7,10 @@ router = APIRouter()
 
 
 @router.post("/deckies/{decky_name}/mutate", tags=["Fleet Management"])
-async def api_mutate_decky(decky_name: str, current_user: str = Depends(get_current_user)) -> dict[str, str]:
+async def api_mutate_decky(
+    decky_name: str = Path(..., pattern=r"^[a-z0-9\-]{1,64}$"),
+    current_user: str = Depends(get_current_user),
+) -> dict[str, str]:
     success = mutate_decky(decky_name)
     if success:
         return {"message": f"Successfully mutated {decky_name}"}