M1-T07: align docs to single-DB reality and re-export OpenAPI

Rewrite README (single app.db + one alembic_app chain, legacy data moved
once via scripts.migrate_legacy_data, accurate test list) and remove the
Grafana Provisioning section. Update architecture-overview to the unified
data layer (one Base, app-DB engine with WAL) and retire the
alembic_location / alembic_poo sections. Mark M1 done in the roadmap.
Re-export openapi/, which catches the spec up to the already-existing
/config/smtp/test and /public-ip/check endpoints (purely additive; M1's
DB-session dependency swap produced no schema change).

pytest 95 passed; ruff clean (pre-existing only); OpenAPI export idempotent.

openapi/openapi.yaml

@@ -155,6 +155,19 @@ paths:
             text/html:
               schema:
                 type: string
+  /config/smtp/test:
+    post:
+      tags:
+      - pages
+      summary: Smtp Test Submit
+      operationId: smtp_test_submit_config_smtp_test_post
+      responses:
+        '200':
+          description: Successful Response
+          content:
+            text/html:
+              schema:
+                type: string
   /homeassistant/publish:
     post:
       tags:
@@ -203,6 +216,19 @@ paths:
           content:
             application/json:
               schema: {}
+  /public-ip/check:
+    get:
+      tags:
+      - public-ip
+      summary: Run Public Ip Check
+      operationId: run_public_ip_check_public_ip_check_get
+      responses:
+        '200':
+          description: Successful Response
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/PublicIPCheckResponse'
   /ticktick/auth/start:
     get:
       tags:
@@ -285,6 +311,29 @@ components:
           title: Detail
       type: object
       title: HTTPValidationError
+    PublicIPCheckResponse:
+      properties:
+        status:
+          type: string
+          enum:
+          - first_seen
+          - unchanged
+          - changed
+          - error
+          title: Status
+        checked_at:
+          type: string
+          format: date-time
+          title: Checked At
+        changed:
+          type: boolean
+          title: Changed
+      type: object
+      required:
+      - status
+      - checked_at
+      - changed
+      title: PublicIPCheckResponse
     StatusResponse:
       properties:
         status: