Add .trivyignore to suppress Dockerfile USER directive finding (DS-0002)

Bambuddy runs as a single-host Docker container where root is needed
for device access and FFmpeg. Trivy picks up the file automatically.

.trivyignore

@@ -0,0 +1,3 @@
+# Dockerfile USER directive (DS-0002): Bambuddy runs as a single-host
+# Docker container where root is needed for device access and FFmpeg.
+DS-0002

CHANGELOG.md

@@ -21,6 +21,28 @@ All notable changes to Bambuddy will be documented in this file.
   - Added pip-audit and npm-audit for dependency vulnerability scanning
   - Automatic GitHub issue creation for detected vulnerabilities
   - Security scan results visible in GitHub Security tab
+- **CodeQL Zero-Finding Baseline**:
+  - Reduced CodeQL findings from 591 to 0 across Python, JavaScript, and GitHub Actions
+  - Created custom query suites (`.codeql/python-bambuddy.qls`, `.codeql/javascript-bambuddy.qls`) with documented accepted-risk exclusions
+  - All exclusions reviewed and justified (log injection parameterized, cyclic imports from SQLAlchemy ORM, intentional 0.0.0.0 binds, etc.)
+- **Log Injection Prevention**:
+  - Converted ~700 f-string log calls to parameterized `%s` style across all backend files
+  - Prevents log injection via newlines or fake log entries in user-controlled data
+- **Exception Handling Hardened**:
+  - Narrowed ~265 bare `except Exception` blocks to specific types (`OSError`, `KeyError`, `ValueError`, `zipfile.BadZipFile`, `sqlalchemy.exc.OperationalError`, etc.)
+- **Stack Trace Exposure Fixed**:
+  - Replaced `str(e)` with generic error messages in HTTP responses (`updates.py`)
+  - Detailed errors still logged server-side for debugging
+- **SSRF Mitigations Added**:
+  - Home Assistant integration: URL scheme/hostname validation, metadata-service blocking (`homeassistant.py`)
+  - Tasmota integration: IP validation blocking loopback and link-local addresses (`tasmota.py`)
+- **Hashlib Security Annotations**:
+  - Added `usedforsecurity=False` to non-security hash calls (MD5 for AMS fingerprinting, SHA1 for git blob format)
+- **Unused Code Removal**:
+  - Removed ~30 redundant function-level imports, unused variables, dead code, and trivial conditions flagged by CodeQL
+- **Local Security Scanner Improvements**:
+  - `test_security.sh` uses `--threads=0` for all CodeQL commands (auto-detects CPU cores)
+  - Added `.trivyignore` to suppress accepted Dockerfile USER directive finding
 
 ### Enhanced
 - **Per-Filament Spoolman Usage Tracking** (PR #277):