fix(build): restore SpotBugs quality gate on main (RAN-26) (#68)

Clears the 13 Medium SpotBugs findings that were failing the gate on main:

- DLS_DEAD_LOCAL_STORE x6 — drop unused `isIndex`/`isEnrich` locals
  in CodeIqApplication; drop dead `fileInventory`/`recoveredEdges`
  locals and the unused `buildFileInventory()` helper (plus its now
  orphaned `FileEntry`/`FileInventory`/`FileClassification` imports)
  in Analyzer; drop dead `flushed`/`recoveredEdges` locals in
  EnrichCommand (replace with a comment documenting why the flush
  + flushDeferred side effects must still run).
- REC_CATCH_EXCEPTION — narrow EnrichCommand top-level catch to
  `IOException | RuntimeException` so unexpected checked types
  surface instead of being silently caught.
- DE/SF (swallow) — FileDiscovery.addGitDiscoveredFile now logs the
  skipped path and IOException cause at debug before returning.
- CT_CONSTRUCTOR_THROW x2 — mark AnalysisCache final so the
  partially-constructed-instance escape path is no longer reachable.
- UC_USELESS_OBJECT x3 — remove the unread `allDetected`/`hookNames`
  set in ReactComponentDetector, the unread `methodPositions` set
  in GoStructuresDetector, and the unread `edgeKinds` map in
  TopologyService#blastRadius.

No behavioural changes; all removals are of values/objects that were
written but never read, and the catch change only widens what
propagates. `mvn spotbugs:check` passes with `BugInstance size = 0`.

Co-authored-by: BackendEngineer (Paperclip agent b94a8dd0)

Co-authored-by: Paperclip <noreply@paperclip.ing>

Author: aksOps