refactor(backend): sanitize user input before logging to close CRLF injection (#807)

* refactor(backend): sanitize user input before logging to close CRLF injection

Adds a small sanitizeForLog helper that strips CR, LF, tab, and ASCII
control characters (0x00-0x1F, 0x7F) from a value before it is embedded
in a console.log/warn/error/debug call. Wraps every call site where a
user-controlled value (req.params, req.body, req.query, or a value
derived from them) flows into a log message.

Closes the bulk of the open CodeQL alerts in this family:
- 96 js/log-injection
- 28 js/tainted-format-string

The helper is in backend/src/utils/safeLog.ts. Routes still pre-validate
input at the request boundary; this is the second line of defense and
gives static analyzers a sanitizer they can trace through. JSON
responses, Docker filter labels, and other non-log call sites are
intentionally left unwrapped.

* refactor(backend): printf-style format strings for tainted-log call sites

CodeQL's js/tainted-format-string rule flags template literals in the first
arg of console.X when any interpolated value is user-controlled, regardless
of whether each value is sanitized inline. The canonical mitigation is to
use a static format string and pass values as positional args.

Converts the 28 flagged template literals to printf-style ("%s") format
strings, with sanitizeForLog applied to each positional arg. Also fills in
the log-injection wraps on 9 sites where a user-controlled value was
missed in the first sweep (agents, fleet, gitSources, imageUpdates,
GitSourceService).

No behavior change at runtime. Node's util.format substitutes %s tokens
identically to template-literal interpolation.

* fix(backend): wrap nodeId/snapshotId in fleet restore debug log

CodeQL flagged the unwrapped numeric args even though they cannot
contain control chars in practice. Apply the sanitizer for taint-flow
recognition.

backend/src/pilot/agent.ts

@@ -13,6 +13,7 @@ import {
     wsDataToBuffer,
     wsDataToString,
 } from './protocol';
+import { sanitizeForLog } from '../utils/safeLog';
 
 const RECONNECT_MIN_MS = 1_000;
 const RECONNECT_MAX_MS = 60_000;
@@ -168,7 +169,7 @@ class PilotAgent {
                 this.handleJsonFrame(frame);
             }
         } catch (err) {
-            console.warn('[Pilot] Malformed frame from primary:', (err as Error).message);
+            console.warn('[Pilot] Malformed frame from primary:', sanitizeForLog((err as Error).message));
         }
     }
 
@@ -178,7 +179,7 @@ class PilotAgent {
         switch (frame.t) {
             case 'hello': {
                 if (frame.version !== PROTOCOL_VERSION) {
-                    console.error(`[Pilot] Protocol version ${frame.version} from primary is incompatible with agent (${PROTOCOL_VERSION}); exiting.`);
+                    console.error(`[Pilot] Protocol version ${sanitizeForLog(frame.version)} from primary is incompatible with agent (${PROTOCOL_VERSION}); exiting.`);
                     this.shuttingDown = true;
                     try { ws.close(1002, 'incompatible version'); } catch { /* ignore */ }
                     process.exit(1);