feat: add fluxer upstream source and self-hosting documentation

- Clone of github.com/fluxerapp/fluxer (official upstream)
- SELF_HOSTING.md: full VM rebuild procedure, architecture overview,
  service reference, step-by-step setup, troubleshooting, seattle reference
- dev/.env.example: all env vars with secrets redacted and generation instructions
- dev/livekit.yaml: LiveKit config template with placeholder keys
- fluxer-seattle/: existing seattle deployment setup scripts

fluxer/.github/ISSUE_TEMPLATE/docs.yml

@@ -0,0 +1,42 @@
+name: Documentation
+description: Report a docs issue or suggest an improvement
+labels: ['docs']
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Thanks.
+
+        Please check our status page at https://fluxerstatus.com and search for existing issues before filing.
+        Security issues should go to https://fluxer.app/security.
+  - type: textarea
+    id: issue
+    attributes:
+      label: What needs fixing?
+      description: Describe the gap, error, or outdated content.
+      placeholder: "The README says ..., but actually ..."
+    validations:
+      required: true
+  - type: textarea
+    id: location
+    attributes:
+      label: Where is it? (optional)
+      description: Link the file/section if possible.
+      placeholder: "File: ...\nSection/heading: ...\nLink: ..."
+    validations:
+      required: false
+  - type: textarea
+    id: suggestion
+    attributes:
+      label: Suggested wording (optional)
+      description: If you already know how it should read, propose text.
+      placeholder: "Proposed text: ..."
+    validations:
+      required: false
+  - type: checkboxes
+    id: checks
+    attributes:
+      label: Checks
+      options:
+        - label: I searched for existing issues and didn't find a duplicate.
+          required: true