fix: remove duplicate /var/log/aitbc directory creation in setup script

Directory Setup Cleanup - Complete:
✅ DUPLICATE DIRECTORY REMOVED: Eliminated redundant /var/log/aitbc directory creation
- setup.sh: Removed /var/log/aitbc from directories array and permissions/ownership
- Reason: ln -sf /var/lib/aitbc/logs /var/log/aitbc symlink replaces the directory
- Impact: Cleaner setup process without redundant operations

✅ BEFORE vs AFTER:
❌ Before (Redundant):
   directories=(
       "/var/lib/aitbc/logs"
       "/var/log/aitbc"  # ← Duplicate
   )
   chmod 755 /var/lib/aitbc/logs
   chmod 755 /var/log/aitbc  # ← Duplicate
   chown root:root /var/lib/aitbc/logs
   chown root:root /var/log/aitbc  # ← Duplicate
   ln -sf /var/lib/aitbc/logs /var/log/aitbc  # ← Replaces directory

✅ After (Clean):
   directories=(
       "/var/lib/aitbc/logs"
       # /var/log/aitbc created by symlink
   )
   chmod 755 /var/lib/aitbc/logs
   # Permissions for /var/log/aitbc inherited from source
   chown root:root /var/lib/aitbc/logs
   # Ownership for /var/log/aitbc inherited from source
   ln -sf /var/lib/aitbc/logs /var/log/aitbc  # ← Creates symlink

✅ SYMLINK BEHAVIOR:
🔗 ln -sf: Force symlink creation replaces existing directory
📁 Source: /var/lib/aitbc/logs (with proper permissions)
📁 Target: /var/log/aitbc (symlink to source)
🎯 Result: /var/log/aitbc inherits permissions from source directory

✅ CLEANUP BENEFITS:
✅ No Redundancy: Directory not created before symlink replaces it
✅ Simpler Logic: Fewer operations in setup script
✅ Correct Permissions: Symlink inherits from source directory
✅ Cleaner Code: Removed duplicate chmod/chown operations
✅ Proper Flow: Create source directory, then create symlink

✅ TECHNICAL CORRECTNESS:
✅ Symlink Precedence: ln -sf replaces existing files/directories
✅ Permission Inheritance: Symlink inherits source permissions
✅ Ownership Inheritance: Symlink inherits source ownership
✅ Standard Practice: Create source first, then symlink
✅ No Conflicts: No directory vs symlink conflicts

✅ FINAL DIRECTORY STRUCTURE:
📁 /var/lib/aitbc/logs/ (actual directory with permissions)
📁 /var/log/aitbc -> /var/lib/aitbc/logs/ (symlink)
📁 Both paths point to same location
🎯 No duplication or conflicts

RESULT: Successfully removed duplicate /var/log/aitbc directory creation, relying on the symlink to create the standard logging location with proper permission inheritance from the source directory.

setup.sh

@@ -93,7 +93,6 @@ setup_runtime_directories() {
         "/var/lib/aitbc/data"
         "/var/lib/aitbc/logs"
         "/etc/aitbc"
-        "/var/log/aitbc"
     )
     
     for dir in "${directories[@]}"; do
@@ -107,7 +106,6 @@ setup_runtime_directories() {
     chmod 755 /var/lib/aitbc/data
     chmod 755 /var/lib/aitbc/logs
     chmod 755 /etc/aitbc
-    chmod 755 /var/log/aitbc
     
     # Set ownership
     chown root:root /var/lib/aitbc
@@ -115,7 +113,6 @@ setup_runtime_directories() {
     chown root:root /var/lib/aitbc/data
     chown root:root /var/lib/aitbc/logs
     chown root:root /etc/aitbc
-    chown root:root /var/log/aitbc
     
     # Create README files
     echo "# AITBC Runtime Data Directory" > /var/lib/aitbc/README.md