Add credentials store to the CRM, docs cleanup, deploy pipeline TODO

Adds a `credentials` entity to the back office (never mirrored to
Sheets, gated by the CRM token even to read) so client logins like
the auto-generated Easy!Appointments provider password can be viewed
and copied from the dashboard instead of getting lost — the actual
cause of the happynails password going missing. Onboarding now saves
that generated password instead of discarding it. Also adds
Documentation.md, brings README/TODO in line with the current
Postgres-first architecture, and tidies the backlog.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

n8n/onboarding.json

@@ -221,7 +221,7 @@
     },
     {
       "parameters": {
-        "jsCode": "const bp=$('EA build provider').first().json;\nconst provId=$json.id;\nconst embed='https://booking.mivanchenko.de/index.php/booking?service='+bp.svcId+'&provider='+provId;\nconst stack_notes='Buchung-Embed: '+embed+' | EA provider '+provId+' / svc '+bp.svcId+' / login '+bp.username;\nreturn [{json:{cid:bp.cid,embed,provId,patch:{stack_notes}}}];"
+        "jsCode": "const bp=$('EA build provider').first().json;\nconst provId=$json.id;\nconst embed='https://booking.mivanchenko.de/index.php/booking?service='+bp.svcId+'&provider='+provId;\nconst stack_notes='Buchung-Embed: '+embed+' | EA provider '+provId+' / svc '+bp.svcId+' / login '+bp.username;\nconst password=bp.providerBody.settings.password;\nreturn [{json:{cid:bp.cid,embed,provId,username:bp.username,password,patch:{stack_notes}}}];"
       },
       "id": "ea-ea-booking-info",
       "name": "EA booking info",
@@ -262,6 +262,37 @@
       "maxTries": 3,
       "waitBetweenTries": 2000,
       "continueOnFail": true
+    },
+    {
+      "parameters": {
+        "options": {},
+        "method": "POST",
+        "url": "http://smb-crm:8080/api/credentials",
+        "sendHeaders": true,
+        "headerParameters": {
+          "parameters": [
+            {
+              "name": "X-CRM-Token",
+              "value": "__CRM_TOKEN__"
+            }
+          ]
+        },
+        "sendBody": true,
+        "specifyBody": "json",
+        "jsonBody": "={{ JSON.stringify({ client_id: $json.cid, label: 'Easy!Appointments Provider-Login', username: $json.username, secret: $json.password }) }}"
+      },
+      "id": "ea-save-credential",
+      "name": "Save credential",
+      "type": "n8n-nodes-base.httpRequest",
+      "typeVersion": 4.2,
+      "position": [
+        1780,
+        680
+      ],
+      "retryOnFail": true,
+      "maxTries": 3,
+      "waitBetweenTries": 2000,
+      "continueOnFail": true
     }
   ],
   "connections": {
@@ -376,6 +407,11 @@
             "node": "EA update client",
             "type": "main",
             "index": 0
+          },
+          {
+            "node": "Save credential",
+            "type": "main",
+            "index": 0
           }
         ]
       ]