fix(security): comprehensive security audit and hardening

Auth: login rate limit 30/min (was 500), global rate limit 1000/min (was
unlimited), password/username max lengths on all Zod schemas, session
invalidation on role change, API key legacy scan bounded to 100 keys.

SVG: hardened regex sanitizer with CDATA stripping, XML entity decoding,
set/animate/iframe/embed blocking, comprehensive data: URI blocking,
use element external href blocking. 11 attack payload fixtures added.

SSRF: fixed DNS rebinding TOCTOU by pinning resolved IPs via custom
HTTP/HTTPS agents. Added 6to4 and NAT64 to blocked IPv6 ranges.

Docker: capability dropping (cap_drop ALL + minimal cap_add), resource
limits (4g/8g mem, 512/1024 pids), healthcheck timeout, password
removed from startup banner, default password warning comments.

Network: CSP and HSTS applied in all environments (not just production),
stack traces removed from all error responses, internal paths stripped
from error details, per-route rate limits on uploads (60/min) and URL
fetches (200/hour).

Files: exclusive temp file creation (O_EXCL), disk space circuit
breaker, per-user storage quotas, settings payload 64KB size guard.

Python sidecar: script name allowlist in dispatcher, minimal environment
for subprocess spawns.

Dependencies: fixed 6 production CVEs (drizzle-orm, fastify, fast-uri,
@fastify/static, next, archiver/lodash). Pinned all GitHub Actions to
SHA hashes.

114 security tests added. Full OWASP Top 10 penetration test matrix
verified against production Docker container (30/30 pass after
hardening).

.github/actions/setup/action.yml

@@ -4,9 +4,9 @@ description: Install pnpm, Node.js 22, and dependencies
 runs:
   using: composite
   steps:
-    - uses: pnpm/action-setup@v4
+    - uses: pnpm/action-setup@b906affcce14559ad1aafd4ab0e942779e9f58b1 # v4
 
-    - uses: actions/setup-node@v4
+    - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
       with:
         node-version: 22
         cache: pnpm