Consolidate dashboards into unified profile page

[realproject7]

Parent Ticket

Merge Writer Dashboard and Reader Dashboard into the Profile page to eliminate duplication and create a single unified user view.

Sub-tickets

1. [#682] Sub-1: Merge Writer Dashboard into Profile Stories tab #683 — Merge Writer Dashboard into Profile Stories tab + remove /writer
2. [#682] Sub-2: Merge Reader Dashboard into Profile Portfolio tab #684 — Merge Reader Dashboard into Profile Portfolio tab + remove /reader
3. [#682] Sub-3: Update nav links, redirects, and cleanup #685 — Update nav links, redirects, cleanup

Execution order

#683 (writer merge) → #684 (reader merge) → #685 (nav + cleanup)

Design decisions

• Own profile: Full dashboard with action buttons (claim royalties, edit genre/language)
• Other's profile: Read-only — storylines, public trades/holdings visible, no action buttons
• Wallet card "0" bug: Fix BigInt(0) rendering as part of this work
• Portfolio tab visible to all: Holdings and trades are on-chain public data
• Activity tab: Unchanged

[realproject7]

All 3 sub-tickets complete: #683 (writer merge), #684 (reader merge), #685 (nav + cleanup). Dashboard consolidation done — 380 lines removed.