chore: consolidate runtime data layout under single data/ root directory

Migrate all runtime artifacts (database, uploads, VAPID keys, locks, bot state, container workspaces, zip staging) from scattered locations (`var/`, `devplacepy/static/uploads/`) into a unified `data/` directory. Update `config.py` as single source of truth with `DATA_PATHS` registry and `ensure_data_dirs()`, add `devplace migrate-data` CLI command with CRC verification and idempotent relocation, adjust `.dockerignore`, `.env.example`, `.gitignore`, `Dockerfile`, `Makefile`, `README.md`, `AGENTS.md`, `CLAUDE.md`, and all import paths in `attachments.py` to reference `config.UPLOADS_DIR`/`ATTACHMENTS_DIR` instead of computing from `STATIC_DIR`.

devplacepy/services/devii/config.py

@@ -6,7 +6,12 @@ import os
 import uuid
 from dataclasses import dataclass
 
-from devplacepy.config import INTERNAL_GATEWAY_URL, INTERNAL_MODEL
+from devplacepy.config import (
+    INTERNAL_GATEWAY_URL,
+    INTERNAL_MODEL,
+    DEVII_TASKS_DB,
+    DEVII_LESSONS_DB,
+)
 
 
 DEFAULT_AI_URL = INTERNAL_GATEWAY_URL
@@ -100,9 +105,9 @@ def load_settings() -> Settings:
         ),
         log_level=os.environ.get("DEVII_LOG_LEVEL", "WARNING").upper(),
         log_path=os.environ.get("DEVII_LOG_PATH", "devii.log"),
-        tasks_db_path=os.environ.get("DEVII_TASKS_DB", "devii_tasks.db"),
+        tasks_db_path=os.environ.get("DEVII_TASKS_DB", str(DEVII_TASKS_DB)),
         scheduler_tick_seconds=float(os.environ.get("DEVII_SCHEDULER_TICK", "1.0")),
-        lessons_db_path=os.environ.get("DEVII_LESSONS_DB", "devii_lessons.db"),
+        lessons_db_path=os.environ.get("DEVII_LESSONS_DB", str(DEVII_LESSONS_DB)),
         delegate_max_iterations=int(
             os.environ.get(
                 "DEVII_DELEGATE_MAX_ITERATIONS", DEFAULT_DELEGATE_MAX_ITERATIONS
@@ -172,7 +177,7 @@ FIELD_RSEARCH_ENABLED = "devii_rsearch_enabled"
 FIELD_RSEARCH_URL = "devii_rsearch_url"
 FIELD_RSEARCH_TIMEOUT = "devii_rsearch_timeout"
 
-LESSONS_DB_PATH = os.environ.get("DEVII_LESSONS_DB", "devii_lessons.db")
+LESSONS_DB_PATH = os.environ.get("DEVII_LESSONS_DB", str(DEVII_LESSONS_DB))
 
 
 def effective_daily_limit(