fix: replace silent catch {} blocks with diagnostic logging

[devin-ai-integration]

Summary

Audited all catch {} blocks across ProfileService, SessionService, and UsageService — 18 total — and replaced each with targeted error handling that logs diagnostic context via console.warn("[keyflow] ...") while preserving existing fallback behavior.

Key patterns applied:

• ENOENT-aware catches: filesystem catches that are expected to hit "file not found" (lock files, config.toml, backup auth, session dirs) now only log on unexpected errors:

  // before
  } catch {}
  // after
  } catch (err: any) {
    if (err?.code !== 'ENOENT') {
      console.warn(`[keyflow] Failed to ...: ${err?.message ?? err}`)
    }
  }

  Applied in: acquireLock stale-lock check, releaseLock, syncCurrentCodexFilesToProfile config.toml copy, pruneBackups, switchToAccount backup, resolveUsageUrl, listFiles, scanLogFile.

• Unconditional logging for non-trivial failures: catches where any error is noteworthy now always log:

  • readState chmod + corrupt-backup, isCodexLinkedSync, saveAuthTokens codex-auth sync, resolveUsageSnapshot token-refresh and email-extraction, session-log parse errors.

• Richer warning in ensureCurrentCodexLinked: the outer catch now distinguishes ENOENT (returns generic "not logged in" message) from other failures (returns Codex auth file could not be read: <message>) so callers/bridge/UI can surface actionable info instead of a misleading "not logged in."

No behavioral changes beyond added logging and the improved ensureCurrentCodexLinked warning message. All existing tests pass; typecheck clean.

Link to Devin session: https://app.devin.ai/sessions/df1ba521fd0c45a5b0a581aa1686652a
Requested by: @hbui290

[devin-ai-integration]

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