fix: resolve all 301 error handling anti-patterns across codebase

Systematic cleanup of every error handling anti-pattern detected by the
automated scanner. 289 issues fixed via code changes, 12 approved with
specific technical justifications.

Changes across 90 files:
- GENERIC_CATCH (141): Added instanceof Error type discrimination
- LARGE_TRY_BLOCK (82): Extracted helper methods to narrow try scope to ≤10 lines
- NO_LOGGING_IN_CATCH (65): Added logger/console calls for error visibility
- CATCH_AND_CONTINUE_CRITICAL_PATH (10): Added throw/return or approved overrides
- ERROR_STRING_MATCHING (2): Approved with rationale (no typed error classes)
- ERROR_MESSAGE_GUESSING (1): Replaced chained .includes() with documented pattern array
- PROMISE_CATCH_NO_LOGGING (1): Added logging to .catch() handler

Also fixes a detector bug where nested try/catch inside a catch block
corrupted brace-depth tracking, causing false positives.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/services/worker/http/routes/ViewerRoutes.ts

@@ -71,7 +71,10 @@ export class ViewerRoutes extends BaseRouteHandler {
     // Guard: if DB is not yet initialized, return 503 before registering client
     try {
       this.dbManager.getSessionStore();
-    } catch {
+    } catch (initError: unknown) {
+      if (initError instanceof Error) {
+        logger.warn('HTTP', 'SSE stream requested before DB initialization', {}, initError);
+      }
       res.status(503).json({ error: 'Service initializing' });
       return;
     }