refactor local directory agent to two-phase LLM-with-tools architecture

Replace the single-pass FE-driven agent_run/agent_data flow with a
BE-orchestrated two-phase execution using LangChain tool-calling:
- Phase 1 (Triage): explores directory via new filesystem tools, matches
  files to existing projects using PROJECT_TOOLS
- Phase 2 (Processing): reads files and performs CRUD per project group
  with clean LLM context windows

Key changes:
- Add filesystem_agent.py with list_directory, read_file_content,
  get_file_metadata tools using execute_on_client()
- Move setup journey from REST to WebSocket (journey_start/message frames)
- Add batch_runs_per_day billing limit and enforce in /trigger
- Remove deprecated agent_data/agent_complete frame handlers and queues

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/billing/tier_manager.py

@@ -21,6 +21,7 @@ FEATURES: dict[str, dict[str, Any]] = {
     "free": {
         "agents": 3,
         "batch_active": 2,
+        "batch_runs_per_day": 5,
         "cloud_storage_gb": 0,
         "backup_gb": 0,
         "providers": 1,
@@ -31,6 +32,7 @@ FEATURES: dict[str, dict[str, Any]] = {
     "pro": {
         "agents": -1,           # unlimited
         "batch_active": 10,
+        "batch_runs_per_day": 50,
         "cloud_storage_gb": 5,
         "backup_gb": 5,
         "providers": -1,
@@ -41,6 +43,7 @@ FEATURES: dict[str, dict[str, Any]] = {
     "power": {
         "agents": -1,
         "batch_active": -1,     # unlimited
+        "batch_runs_per_day": -1,  # unlimited
         "cloud_storage_gb": 25,
         "backup_gb": 25,
         "providers": -1,
@@ -51,6 +54,7 @@ FEATURES: dict[str, dict[str, Any]] = {
     "team": {
         "agents": -1,
         "batch_active": -1,
+        "batch_runs_per_day": -1,  # unlimited
         "cloud_storage_gb": -1,  # unlimited
         "backup_gb": -1,         # unlimited
         "providers": -1,