Fix system prompt leakage into chat history; polish content cards ...

Backend:
- websocket.py + agent.py: separate user-visible display_message from
  LLM user_message. System hints (image/file attachments) no longer leak
  into session.messages and appear after page reload.
- main.py: add ensure_tables() on startup so session_content table is
  created before first publish.
- profiles: add kimi-k2.6:cloud to all model lists as fallback.

Frontend:
- ContentCard.vue: remove border-radius, add scrollbar styles, fix
  metadata fallback parsing so cards survive page reload.
- content-viewers/*.html: add matching scrollbar styles.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

changed llm

changed llm & new ollama param

changed model

Tune profile sampling configs

temp -

Set temperature=1.0, top_k=64, top_p=0.95 for all profiles (Google recommended for gemma4) ...

Also fixes discuss profile memory tools: use combined "memory" tool name, not nonexistent split variants.

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

Fix discuss profile planning: phase1 on (DIRECT gate), phase3 off ...

Model can skip planning via DIRECT; if it doesn't, analysis runs silently
without producing a plan card in the UI.

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

Add discuss profile; responsive WelcomeScreen for 6+ profiles ...

- New 'discuss' profile: creative Q&A and idea discussion, temp=1.0,
  planning phase 3 only, tools: web_search/view, scratchpad, reflect,
  memory, image_view, todo
- WelcomeScreen mobile: 2-column grid for profile cards, compact logo
  (row layout with subtitle on second line), reduced padding/gaps

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